tools/serve.py: build, serve and rebuild on change (t9)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tasks/t9_script_run_local.md

@@ -1,11 +1,23 @@
 ---
 id: t9
 title: Script to run the local server for testing
-status: Todo
+status: Review
 created: 2026-10-24
-updated: 2026-10-24T04:41:46Z
+updated: 2026-10-24T05:06:19Z
+order: 3
+report: |
+  (agent) New: python3 tools/serve.py builds the game, serves it at http://localhost:8000 and
+  rebuilds by itself when anything in src/ changes. Pages aren't cached, so a normal refresh
+  shows the new build. If 8000 is taken (an old server still running), it uses 8001 and says so.
+  To check: stop your old server (Ctrl+C), run python3 tools/serve.py, open the address it
+  prints, change something in src/, refresh. Ctrl+C stops it.
 ---
 
 ## Context
 
 - i need a script to run the local server for testing.
+
+## Subtasks
+
+- [x] Add the server and update the command references and map.
+- [x] Check serving, rebuilds, port fallback and shutdown; run the headless suites.