docs: update for codebase consolidation and startup fixes

- Remove source.py from architecture (deleted)
- Add metrics.py to module list
- Update warm start: trusts cached state, instant startup
- Update signal handling: registered before startup
- Add refactoring tasks to TASKS.md
- Remove stale troubleshooting entry

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/CHEATSHEET.md

@@ -123,7 +123,6 @@ metrics: conn=142 ok=98 fail=44 retries=88 active=3 in=1.2M out=4.5M up=0h05m12s
 | DNS leak | Use `socks5h://` (not `socks5://`) in client |
 | Auth failed | Verify credentials in proxy URL |
 | Port in use | `fuser -k 1080/tcp` to free the port |
-| Container slow stop | Rebuild image after SIGTERM fix |
 | Proxy keeps failing | Backoff penalizes for 60s; check `pool=` in metrics |
 | "static chain unreachable" | Tor/upstream hop is down; pool tests skipped |
-| Slow startup | Normal on cold start; warm restarts use state file |
+| Slow startup | Normal on cold start; warm restarts serve instantly from state |

docs/USAGE.md

@@ -179,11 +179,10 @@ are loaded for fast warm starts.
 
 ### Warm start
 
-When restarting with an existing state file, only the previously-alive proxies
-are tested before the server starts accepting connections. A full health test
-of all proxies runs in the background. This reduces startup blocking from
-minutes to seconds on warm restarts. Cold starts (no state file) test all
-proxies before serving.
+When restarting with an existing state file, the server trusts the cached
+alive state and begins accepting connections immediately. A full health test
+of all proxies runs in the background. Startup takes seconds regardless of
+pool size. Cold starts (no state file) test all proxies before serving.
 
 ### Dead proxy reporting