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>

Dockerfile

@@ -12,6 +12,7 @@ COPY Pipfile Pipfile.lock ./
 RUN pipenv install --system --deploy
 
 COPY src ./src
+COPY lib ./lib
 COPY workspace ./workspace
 
 EXPOSE 8080