Ship MicroPython stubs from repo lib/ and seed workspace lib on startup

Move machine.py and neopixel.py into a tracked /lib/ at the repo root and
auto-copy them into WORKSPACE_ROOT/lib whenever files are missing, so empty
volumes and fresh per-user workspaces always have the read-only stubs
available to Jedi and Pyodide. Allow all users to browse lib/ in the UI
(writes still gated by the API), and add tests covering initial seeding
and re-population after the dir is wiped.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/static/index.html

@@ -87,6 +87,6 @@
     </div>
   </div>
 
-  <script type="module" src="/static/script.js?v=25"></script>
+  <script type="module" src="/static/script.js?v=26"></script>
 </body>
 </html>