docs: add agent tracking files, update task management and dev checklist to .github folder

.github/AGENTS.md

@@ -14,9 +14,29 @@ Agents instructions for the linearvoid project.
 
 ## Task Management
 
-- Plan any task in the `TODO.md` file with clear steps and mark them as completed when done. Move completed sections to DONE.md. Write entry in root `CHANGELOG.md` for any significant changes. Avoid using in-memory todo lists or update them frequently to sync from the `TODO.md` file.
+- Plan any task in the `.github/instructions/TODO.md` file with clear steps and mark them as completed when done. Move completed sections to `.github/instructions/DONE.md`. Write entry in root `CHANGELOG.md` for any significant changes. Avoid using in-memory todo lists or update them frequently to sync from the `TODO.md` file.
 - Before taking any action except for planning and writing `TODO.md`, always ask user for confirmation, accept `go`, `ok`, `yes`, `next`, or `continue` to proceed. If the user says `no`, `stop`, or `cancel`, abort the action and return to planning.
 
+### Required tracking files — update at every development step
+
+These files must be kept current with every change. Do not let them drift.
+
+| File                              | Purpose                                       | When to update                                                     |
+| --------------------------------- | --------------------------------------------- | ------------------------------------------------------------------ |
+| `.github/instructions/TODO.md`    | Active implementation plan with checkboxes    | Mark items done as they complete; add new items when scope expands |
+| `.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            |
+| `docs/SETUP.md`                   | Environment and onboarding guide              | Update when prerequisites, `.env`, or setup steps change           |
+| `docs/MONITORING.md`              | Observability reference                       | Update when metrics, alerts, or dashboards change                  |
+| `docs/API.md`                     | API contract                                  | Update when endpoints, status codes, or rate limits change         |
+| `docs/SECURITY.md`                | Security posture                              | Update when auth, TLS, or rate limiting changes                    |
+| `docs/operations/*.md`            | Runbooks, checklists, how-to guides           | Keep aligned with actual procedures and dashboard URLs             |
+
 ## Security & Secrets Protection
 
 - **Never commit raw secrets or credentials** to the repository.