chore(changelog): retire CHANGELOG.md as a dependency

The update dialog (server and desktop) now reads changelog/index.json and
renders title, intro and groups; the release workflow builds the GitHub
Release body and name from changelog/<version>.md; oc-dev, the issue-intake
agent, AGENTS.md and the changelog skill no longer point at the file.

CHANGELOG.md stays as a legacy copy for installs up to 1.22.1, which fetch
it for update notes. The generator refreshes it while it exists and never
recreates it, so deleting it after 2026-09-19 retires it for good.

Generated outputs hold released versions only, so editing unreleased.md
never makes them stale: agents write that file and nothing else, and
oc-dev create-release does the generation.

Claude-Session: https://claude.ai/code/session_01VqV56Hez25hTxXH4ipJfzH

.github/workflows/release.yml

@@ -48,26 +48,12 @@ jobs:
           fi
 
       - name: Extract changelog for release
+        id: release_notes
         env:
           VERSION: ${{ steps.get_version.outputs.version }}
         run: |
-          node - <<'NODE'
-          const fs = require('fs');
-          const version = process.env.VERSION;
-          const changelogPath = 'CHANGELOG.md';
-          if (!fs.existsSync(changelogPath)) {
-            throw new Error('CHANGELOG.md not found; add it before releasing.');
-          }
-          const changelog = fs.readFileSync(changelogPath, 'utf8');
-          const sections = changelog.split(/^## /m);
-          const section = sections.find(s => s.startsWith('[' + version + ']'));
-          if (!section) {
-            throw new Error('Changelog section [' + version + '] not found. Add a section like "## [' + version + '] - YYYY-MM-DD".');
-          }
-          const content = ('## ' + section).trim();
-          fs.mkdirSync('artifacts', { recursive: true });
-          fs.writeFileSync('artifacts/release-notes.md', content + '\n');
-          NODE
+          title=$(node scripts/changelog/release-notes.mjs "$VERSION" artifacts/release-notes.md)
+          echo "name=OpenChamber v$VERSION: $title" >> "$GITHUB_OUTPUT"
 
       - name: Create GitHub Release
         id: create_release
@@ -77,7 +63,7 @@ jobs:
           draft: true
           generate_release_notes: false
           body_path: artifacts/release-notes.md
-          name: OpenChamber v${{ steps.get_version.outputs.version }}
+          name: ${{ steps.release_notes.outputs.name }}
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}