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>

lib/machine.py

@@ -0,0 +1,19 @@
+"""Minimal MicroPython-style machine module mock for browser simulation."""
+
+
+class Pin:
+    IN = 0
+    OUT = 1
+    PULL_UP = 2
+    PULL_DOWN = 3
+
+    def __init__(self, pin_id: int, mode: int = OUT, value: int = 0):
+        self.id = int(pin_id)
+        self.mode = int(mode)
+        self._value = 1 if value else 0
+
+    def value(self, new_value=None):
+        if new_value is None:
+            return self._value
+        self._value = 1 if int(new_value) else 0
+        return self._value