feat: extract CHANGELOG_WORKFLOW resolver from /ship

Move changelog generation logic into a reusable resolver. The resolver
is changelog-only (no version bump per Codex review recommendation).
Adds voice rules inline. /ship Step 5 now uses {{CHANGELOG_WORKFLOW}}.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ship/SKILL.md

@@ -1714,7 +1714,7 @@ already knows. A good test: would this insight save time in a future session? If
 
 ---
 
-## Step 5: CHANGELOG (auto-generate)
+## CHANGELOG (auto-generate)
 
 1. Read `CHANGELOG.md` header to know the format.
 
@@ -1747,6 +1747,7 @@ already knows. A good test: would this insight save time in a future session? If
    - Write concise, descriptive bullet points
    - Insert after the file header (line 5), dated today
    - Format: `## [X.Y.Z.W] - YYYY-MM-DD`
+   - **Voice:** Lead with what the user can now **do** that they couldn't before. Use plain language, not implementation details. Never mention TODOS.md, internal tracking, or contributor-facing details.
 
 6. **Cross-check:** Compare your CHANGELOG entry against the commit list from step 2.
    Every commit must map to at least one bullet point. If any commit is unrepresented,

ship/SKILL.md.tmpl

@@ -342,46 +342,7 @@ For each classified comment:
 
 ---
 
-## Step 5: CHANGELOG (auto-generate)
-
-1. Read `CHANGELOG.md` header to know the format.
-
-2. **First, enumerate every commit on the branch:**
-   ```bash
-   git log <base>..HEAD --oneline
-   ```
-   Copy the full list. Count the commits. You will use this as a checklist.
-
-3. **Read the full diff** to understand what each commit actually changed:
-   ```bash
-   git diff <base>...HEAD
-   ```
-
-4. **Group commits by theme** before writing anything. Common themes:
-   - New features / capabilities
-   - Performance improvements
-   - Bug fixes
-   - Dead code removal / cleanup
-   - Infrastructure / tooling / tests
-   - Refactoring
-
-5. **Write the CHANGELOG entry** covering ALL groups:
-   - If existing CHANGELOG entries on the branch already cover some commits, replace them with one unified entry for the new version
-   - Categorize changes into applicable sections:
-     - `### Added` — new features
-     - `### Changed` — changes to existing functionality
-     - `### Fixed` — bug fixes
-     - `### Removed` — removed features
-   - Write concise, descriptive bullet points
-   - Insert after the file header (line 5), dated today
-   - Format: `## [X.Y.Z.W] - YYYY-MM-DD`
-
-6. **Cross-check:** Compare your CHANGELOG entry against the commit list from step 2.
-   Every commit must map to at least one bullet point. If any commit is unrepresented,
-   add it now. If the branch has N commits spanning K themes, the CHANGELOG must
-   reflect all K themes.
-
-**Do NOT ask the user to describe changes.** Infer from the diff and commit history.
+{{CHANGELOG_WORKFLOW}}
 
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