Add release skill for Claude Code (#1800)

## Summary
- Adds a `/release` Claude Code skill that documents the lading release process
- Covers: changelog update, version bump, lockfile sync via `cargo check`, commit, tag, and push

## Test plan
- [x] Verify skill appears in `/release` invocation
- [ ] Use skill to perform the 0.31.0 release on a separate branch

Author: GeorgeHahn

.claude/skills/release/SKILL.md

@@ -0,0 +1,49 @@
+---
+name: release
+description: Prepare a lading release. Updates CHANGELOG.md, bumps version in Cargo.toml, updates Cargo.lock, commits, and creates a PR.
+allowed-tools: Read, Edit, Bash, AskUserQuestion
+---
+
+# Release process for lading
+
+## 1. Determine the next version
+
+- Read `lading/Cargo.toml` and `CHANGELOG.md` to find the current version and unreleased changes.
+- If the user hasn't specified a version, suggest one based on semver:
+  - Breaking changes in the unreleased section -> bump minor (we're pre-1.0).
+  - Otherwise bump patch.
+- Confirm the version with the user before proceeding.
+
+## 2. Create a release branch
+
+- Create a branch from main: `git checkout -b prepare-release-v<version>`
+
+## 3. Update CHANGELOG.md
+
+- Read `CHANGELOG.md`.
+- Insert a new `## Unreleased` header (with empty subsections) above the current unreleased content.
+- Rename the existing unreleased content block to `## [<version>]`.
+- Ensure there is a blank line between the new empty `## Unreleased` and `## [<version>]`.
+
+## 4. Bump version in Cargo.toml
+
+- Edit `lading/Cargo.toml` to set `version = "<new_version>"`.
+
+## 5. Update Cargo.lock
+
+- Run `cargo check` to propagate the version change into the lockfile without re-resolving all dependencies.
+
+## 6. Commit and create PR
+
+- Stage `CHANGELOG.md`, `lading/Cargo.toml`, and `Cargo.lock`.
+- Commit with message: `release: v<version>`
+- Push the branch and create a PR targeting main.
+
+## 7. Tag after merge
+
+- After the PR is merged, remind the user to tag the merge commit on main:
+  - `git checkout main && git pull`
+  - `git tag -a v<version> -m "v<version>"`
+  - `git push origin v<version>`
+- **NEVER use `git push --tags`** — always push exactly one tag at a time.
+- The `release.yml` GitHub Actions workflow will automatically create a GitHub Release from the tag, pulling notes from CHANGELOG.md.