chore: remove obsolete DEVELOPMENT.md and consolidate task tracking docs

.github/AGENTS.md

@@ -23,7 +23,6 @@ These files must be kept current with every change. Do not let them drift.
 | `.github/instructions/BACKLOG.md` | Deferred, manual, and operational tasks       | Sync whenever TODO items complete or new gaps are identified       |
 | `.github/instructions/DONE.md`    | Archive of completed TODO sections            | Move completed sections here from TODO.md                          |
 | `.github/MEMORY.md`               | Session memory — what was done, when, and why | Append dated entry after each meaningful batch of changes          |
-| `docs/DEVELOPMENT.md`             | Remaining task checklist organized by topic   | Sync checkboxes with TODO.md after each implementation session     |
 | `CHANGELOG.md`                    | User-facing release notes                     | Add entry when a phase or significant feature completes            |
 | `docs/STREAMING.md`               | Streaming pipeline contract                   | Update when playout, HLS, or caching behavior changes              |
 | `docs/DEPLOYMENT.md`              | Deploy and infrastructure procedures          | Update when pipeline, topology, or provisioning changes            |