add release skills, backfill changelog, wire CI to use changelog for GitHub releases

- Backfill CHANGELOG.md from all 17 GitHub releases (was stale at v0.1.0)
- Add draft-release-notes and release-bump agent skills
- Extract release notes from CHANGELOG.md in release CI instead of hardcoded placeholder
- Remove stale PATCH_NOTES.md, mlx-test/, move PROJECT_STATUS to docs/notes
- Reorganize API reference docs from unknown/ to named groups
- Update openapi.json

docs/content/docs/api-reference/models/meta.json

@@ -0,0 +1,10 @@
+{
+  "title": "Models",
+  "pages": [
+    "get_model_status_models_status_get",
+    "load_model_models_load_post",
+    "unload_model_models_unload_post",
+    "trigger_model_download_models_download_post",
+    "get_model_progress_models_progress__model_name__get"
+  ]
+}