feat: add JS-style changeset workflow

This implements the changeset workflow similar to JavaScript's @changesets/cli:

- Add .changeset/ folder structure with config.json and README.md
- Update create-manual-changeset.mjs for JS-style format with frontmatter
- Update validate-changeset.mjs to validate the new changeset format
- Add merge-changesets.mjs to merge multiple changesets (highest bump wins)
- Update collect-changelog.mjs to work with the new format
- Update version-and-commit.mjs with changeset mode for auto version bump
- Update release.yml with changeset, instant, and changeset-pr modes
- Update README.md and CONTRIBUTING.md with new workflow documentation
- Remove old changelog.d/ folder

The changeset workflow:
- Avoids merge conflicts on CHANGELOG.md
- Automatically determines version bump from changesets
- Matches the pattern used in the JS template

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: konard

.changeset/README.md

@@ -0,0 +1,78 @@
+# Changesets
+
+This directory contains changeset files that document changes for upcoming releases.
+
+## Why Changesets?
+
+Using individual changeset files instead of editing `CHANGELOG.md` directly:
+- **Avoids merge conflicts** when multiple PRs are open
+- **Associates changes with PRs** for better traceability
+- **Enforces documentation** of all changes
+- **Determines version bump type** automatically from the changesets
+
+## Creating a Changeset
+
+### Using the Script
+
+```bash
+# Create a new changeset
+bun scripts/create-manual-changeset.mjs --bump-type patch --description "Fix a bug"
+bun scripts/create-manual-changeset.mjs --bump-type minor --description "Add new feature"
+bun scripts/create-manual-changeset.mjs --bump-type major --description "Breaking change"
+```
+
+### Manually
+
+Create a file with a random name (e.g., `happy-cats-dance.md`) in this directory with the following format:
+
+```markdown
+---
+'java-ai-driven-development-pipeline-template': patch
+---
+
+Description of the changes made.
+```
+
+## Changeset Format
+
+Each changeset file has two parts:
+
+1. **Frontmatter** (between `---` markers):
+   - Package name and version bump type (major, minor, or patch)
+
+2. **Description**:
+   - Clear description of what changed
+   - Use present tense ("Add feature" not "Added feature")
+   - Reference issue numbers when applicable: "Fix login bug (#123)"
+
+### Version Bump Types
+
+- **patch**: Bug fixes, documentation updates, internal changes
+- **minor**: New features, non-breaking enhancements
+- **major**: Breaking changes, API changes
+
+## Example Changeset
+
+```markdown
+---
+'java-ai-driven-development-pipeline-template': minor
+---
+
+Add async delay function with CompletableFuture support for non-blocking operations.
+```
+
+## What Happens During Release
+
+1. The release workflow detects pending changesets
+2. Multiple changesets are merged (highest bump type wins)
+3. Version is bumped according to the determined bump type
+4. A new version entry is added to `CHANGELOG.md`
+5. Changeset files are deleted
+6. Changes are committed and pushed to main
+
+## Tips
+
+- One changeset per PR is typical
+- Be concise but descriptive in your descriptions
+- The bump type determines the version number change
+- Multiple changesets are automatically merged during release

.changeset/brave-tigers-dance.md

@@ -0,0 +1,13 @@
+---
+'my-package': minor
+---
+
+Add JS-style changeset workflow for managing version bumps and changelogs.
+
+This implementation:
+- Uses `.changeset/` folder structure similar to JavaScript's `@changesets/cli`
+- Changeset files include package name and bump type in frontmatter
+- Automatically determines version bump from changesets (highest type wins)
+- Merges multiple changesets during release
+- Supports three release modes: changeset, instant, and changeset-pr
+- Eliminates merge conflicts on CHANGELOG.md

.changeset/config.json

@@ -0,0 +1,10 @@
+{
+  "changelog": false,
+  "commit": false,
+  "fixed": [],
+  "linked": [],
+  "access": "public",
+  "baseBranch": "main",
+  "updateInternalDependencies": "patch",
+  "ignore": []
+}

.github/workflows/release.yml

@@ -7,15 +7,28 @@ on:
     types: [opened, synchronize, reopened]
   workflow_dispatch:
     inputs:
-      bump_type:
-        description: 'Version bump type'
+      release_mode:
+        description: 'Release mode'
         required: true
+        default: 'changeset'
+        type: choice
+        options:
+          - changeset
+          - instant
+          - changeset-pr
+      bump_type:
+        description: 'Version bump type (for instant mode or changeset-pr)'
+        required: false
         default: 'patch'
         type: choice
         options:
           - patch
           - minor
           - major
+      description:
+        description: 'Change description (for changeset-pr mode)'
+        required: false
+        type: string
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}
@@ -129,10 +142,10 @@ jobs:
           retention-days: 7
 
   # =============================================================================
-  # Changelog Fragment Validation (PRs only)
+  # Changeset Validation (PRs only)
   # =============================================================================
-  changelog-check:
-    name: Changelog Check
+  changeset-check:
+    name: Changeset Check
     runs-on: ubuntu-latest
     if: github.event_name == 'pull_request'
     steps:
@@ -146,13 +159,13 @@ jobs:
         with:
           bun-version: latest
 
-      - name: Validate changelog fragment
+      - name: Validate changeset
         run: bun scripts/validate-changeset.mjs
         env:
           GITHUB_BASE_REF: ${{ github.base_ref }}
 
   # =============================================================================
-  # Auto Release (on push to main)
+  # Auto Release (on push to main with changesets)
   # =============================================================================
   auto-release:
     name: Auto Release
@@ -166,6 +179,7 @@ jobs:
         uses: actions/checkout@v4
         with:
           fetch-depth: 0
+          token: ${{ secrets.GITHUB_TOKEN }}
 
       - name: Set up JDK ${{ env.JAVA_VERSION }}
         uses: actions/setup-java@v4
@@ -179,54 +193,118 @@ jobs:
         with:
           bun-version: latest
 
-      - name: Get current version
-        id: version
-        run: |
-          VERSION=$(mvn help:evaluate -Dexpression=project.version -q -DforceStdout)
-          echo "version=$VERSION" >> $GITHUB_OUTPUT
-          echo "Current version: $VERSION"
-
-      - name: Check if tag exists
-        id: tag_check
+      - name: Check for changesets
+        id: changesets
         run: |
-          TAG="v${{ steps.version.outputs.version }}"
-          if git rev-parse "$TAG" >/dev/null 2>&1; then
-            echo "exists=true" >> $GITHUB_OUTPUT
-            echo "Tag $TAG already exists"
+          CHANGESET_COUNT=$(find .changeset -name "*.md" ! -name "README.md" 2>/dev/null | wc -l)
+          echo "count=$CHANGESET_COUNT" >> $GITHUB_OUTPUT
+          if [ "$CHANGESET_COUNT" -gt 0 ]; then
+            echo "has_changesets=true" >> $GITHUB_OUTPUT
+            echo "Found $CHANGESET_COUNT changeset(s)"
           else
-            echo "exists=false" >> $GITHUB_OUTPUT
-            echo "Tag $TAG does not exist"
+            echo "has_changesets=false" >> $GITHUB_OUTPUT
+            echo "No changesets found"
           fi
 
+      - name: Merge changesets (if multiple)
+        if: steps.changesets.outputs.has_changesets == 'true' && steps.changesets.outputs.count > 1
+        run: bun scripts/merge-changesets.mjs
+
+      - name: Run version and commit script
+        if: steps.changesets.outputs.has_changesets == 'true'
+        id: release
+        run: bun scripts/version-and-commit.mjs --mode changeset
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Build release artifacts
+        if: steps.release.outputs.released == 'true'
+        run: mvn package source:jar javadoc:jar -DskipTests -B
+
+      - name: Create GitHub Release
+        if: steps.release.outputs.released == 'true'
+        run: |
+          bun scripts/create-github-release.mjs \
+            --release-version "${{ steps.release.outputs.new_version }}" \
+            --repository "${{ github.repository }}"
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Upload release artifacts
+        if: steps.release.outputs.released == 'true'
+        run: |
+          TAG="v${{ steps.release.outputs.new_version }}"
+          gh release upload "$TAG" target/*.jar --clobber || true
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+  # =============================================================================
+  # Manual Release - Changeset Mode (workflow dispatch)
+  # =============================================================================
+  manual-release-changeset:
+    name: Manual Release (Changeset)
+    runs-on: ubuntu-latest
+    needs: [build]
+    if: github.event_name == 'workflow_dispatch' && github.event.inputs.release_mode == 'changeset'
+    permissions:
+      contents: write
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+          token: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Set up JDK ${{ env.JAVA_VERSION }}
+        uses: actions/setup-java@v4
+        with:
+          java-version: ${{ env.JAVA_VERSION }}
+          distribution: ${{ env.JAVA_DISTRIBUTION }}
+          cache: maven
+
+      - name: Set up Bun
+        uses: oven-sh/setup-bun@v2
+        with:
+          bun-version: latest
+
+      - name: Merge changesets (if multiple)
+        run: bun scripts/merge-changesets.mjs
+
+      - name: Run version and commit script
+        id: release
+        run: bun scripts/version-and-commit.mjs --mode changeset
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
       - name: Build release artifacts
-        if: steps.tag_check.outputs.exists == 'false'
+        if: steps.release.outputs.released == 'true'
         run: mvn package source:jar javadoc:jar -DskipTests -B
 
       - name: Create GitHub Release
-        if: steps.tag_check.outputs.exists == 'false'
+        if: steps.release.outputs.released == 'true'
         run: |
           bun scripts/create-github-release.mjs \
-            --release-version "${{ steps.version.outputs.version }}" \
+            --release-version "${{ steps.release.outputs.new_version }}" \
             --repository "${{ github.repository }}"
         env:
           GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
 
       - name: Upload release artifacts
-        if: steps.tag_check.outputs.exists == 'false'
+        if: steps.release.outputs.released == 'true'
         run: |
-          TAG="v${{ steps.version.outputs.version }}"
+          TAG="v${{ steps.release.outputs.new_version }}"
           gh release upload "$TAG" target/*.jar --clobber || true
         env:
           GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
 
   # =============================================================================
-  # Manual Release (workflow dispatch)
+  # Manual Release - Instant Mode (workflow dispatch)
   # =============================================================================
-  manual-release:
-    name: Manual Release
+  manual-release-instant:
+    name: Manual Release (Instant)
     runs-on: ubuntu-latest
     needs: [build]
-    if: github.event_name == 'workflow_dispatch'
+    if: github.event_name == 'workflow_dispatch' && github.event.inputs.release_mode == 'instant'
     permissions:
       contents: write
     steps:
@@ -250,7 +328,7 @@ jobs:
 
       - name: Run version and commit script
         id: release
-        run: bun scripts/version-and-commit.mjs --bump-type ${{ inputs.bump_type }}
+        run: bun scripts/version-and-commit.mjs --mode instant --bump-type ${{ inputs.bump_type }}
         env:
           GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
 
@@ -274,3 +352,55 @@ jobs:
           gh release upload "$TAG" target/*.jar --clobber || true
         env:
           GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+  # =============================================================================
+  # Manual Changeset PR (workflow dispatch)
+  # =============================================================================
+  changeset-pr:
+    name: Create Changeset PR
+    runs-on: ubuntu-latest
+    if: github.event_name == 'workflow_dispatch' && github.event.inputs.release_mode == 'changeset-pr'
+    permissions:
+      contents: write
+      pull-requests: write
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Set up Bun
+        uses: oven-sh/setup-bun@v2
+        with:
+          bun-version: latest
+
+      - name: Create changeset file
+        run: |
+          DESCRIPTION="${{ inputs.description }}"
+          if [ -z "$DESCRIPTION" ]; then
+            DESCRIPTION="Manual release"
+          fi
+          bun scripts/create-manual-changeset.mjs \
+            --bump-type "${{ inputs.bump_type }}" \
+            --description "$DESCRIPTION"
+
+      - name: Create Pull Request
+        uses: peter-evans/create-pull-request@v6
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          commit-message: "chore: add changeset for ${{ inputs.bump_type }} release"
+          branch: changeset-manual-release-${{ github.run_id }}
+          delete-branch: true
+          title: "chore: ${{ inputs.bump_type }} release changeset"
+          body: |
+            ## Summary
+
+            This PR adds a changeset for a **${{ inputs.bump_type }}** release.
+
+            ${{ inputs.description }}
+
+            ---
+            *This PR was automatically created by the changeset-pr workflow.*
+          labels: |
+            release
+            automated