chore(ci): rationalize CI into single workflow with unified comment

Merge three separate CI actions (incremental-build, detect-dependencies,
component-test) into one unified incremental-build script and simplify
the workflow architecture.

Deleted:
  .github/actions/component-test/
  .github/actions/detect-dependencies/

Added:
  .github/workflows/pr-test-commenter.yml
  .github/CI-ARCHITECTURE.md

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: gnodet

.github/CI-ARCHITECTURE.md

@@ -0,0 +1,110 @@
+# CI Architecture
+
+Overview of the GitHub Actions CI/CD ecosystem for Apache Camel.
+
+## Workflow Overview
+
+```
+PR opened/updated
+       │
+       ├──► pr-id.yml ──► pr-commenter.yml (welcome message)
+       │
+       └──► pr-build-main.yml (Build and test)
+                │
+                ├── regen.sh (full build, no tests)
+                ├── incremental-build (test affected modules)
+                │       ├── File-path analysis
+                │       ├── POM dependency analysis (Toolbox)
+                │       └── Extra modules (/component-test)
+                │
+                └──► pr-test-commenter.yml (post unified comment)
+
+PR comment: /component-test kafka http
+       │
+       └──► pr-manual-component-test.yml
+                │
+                └── dispatches "Build and test" with extra_modules
+```
+
+## Workflows
+
+### `pr-build-main.yml` — Build and test
+- **Trigger**: `pull_request` (main branch), `workflow_dispatch`
+- **Matrix**: JDK 17, 21, 25 (25 is experimental)
+- **Steps**:
+  1. Full build via `regen.sh` (`mvn install -DskipTests -Pregen`)
+  2. Check for uncommitted generated files
+  3. Run incremental tests (only affected modules)
+  4. Upload test comment as artifact
+- **Inputs** (workflow_dispatch): `pr_number`, `pr_ref`, `extra_modules`
+
+### `pr-test-commenter.yml` — Post CI test comment
+- **Trigger**: `workflow_run` on "Build and test" completion
+- **Purpose**: Posts the unified test summary comment on the PR
+- **Why separate**: Uses `workflow_run` to run in base repo context, allowing
+  comment posting on fork PRs (where `GITHUB_TOKEN` is read-only)
+
+### `pr-manual-component-test.yml` — /component-test handler
+- **Trigger**: `issue_comment` with `/component-test` prefix
+- **Who**: MEMBER, OWNER, or CONTRIBUTOR only
+- **What**: Resolves component names to module paths, dispatches the main
+  "Build and test" workflow with `extra_modules`
+
+### `pr-id.yml` + `pr-commenter.yml` — Welcome message
+- **Trigger**: `pull_request` (all branches)
+- **Purpose**: Posts the one-time welcome message on new PRs
+- **Why two workflows**: `pr-id.yml` runs in PR context (uploads PR number),
+  `pr-commenter.yml` runs via `workflow_run` with write permissions
+
+### `main-build.yml` — Main branch build
+- **Trigger**: `push` to main, camel-4.14.x, camel-4.18.x
+- **Steps**: Same as PR build but without comment posting
+
+### Other workflows
+- `pr-labeler.yml` — Auto-labels PRs based on changed files
+- `pr-doc-validation.yml` — Validates documentation changes
+- `pr-cleanup-branches.yml` — Cleans up merged PR branches
+- `alternative-os-build-main.yml` — Tests on non-Linux OSes
+- `check-container-versions.yml` — Checks test container version updates
+- `generate-sbom-main.yml` — Generates SBOM for releases
+- `security-scan.yml` — Security vulnerability scanning
+
+## Actions
+
+### `incremental-build`
+The core test runner. Determines which modules to test using:
+1. **File-path analysis**: Maps changed files to Maven modules
+2. **POM dependency analysis**: For changed `pom.xml` files, detects property
+   changes and uses [Maveniverse Toolbox](https://github.com/maveniverse/toolbox)
+   `tree-find` to discover modules depending on affected artifacts (including
+   transitive dependencies)
+3. **Extra modules**: Additional modules passed via `/component-test`
+
+Results are merged, deduplicated, and tested. The script also:
+- Detects tests disabled in CI (`@DisabledIfSystemProperty(named = "ci.env.name")`)
+- Applies an exclusion list for generated/meta modules
+- Generates a unified PR comment with all test information
+
+### `install-mvnd`
+Installs the Maven Daemon (mvnd) for faster builds.
+
+### `install-packages`
+Installs system packages required for the build.
+
+## PR Labels
+
+| Label | Effect |
+|-------|--------|
+| `skip-tests` | Skip all tests |
+| `test-dependents` | Force testing dependent modules even if threshold exceeded |
+
+## CI Environment
+
+The CI sets `-Dci.env.name=github.com` via `MVND_OPTS` (in `install-mvnd`).
+Tests can use `@DisabledIfSystemProperty(named = "ci.env.name")` to skip
+flaky tests in CI. The test comment warns about these skipped tests.
+
+## Comment Markers
+
+PR comments use HTML markers for upsert (create-or-update) behavior:
+- `<!-- ci-tested-modules -->` — Unified test summary comment