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/script.js

@@ -293,9 +293,6 @@ class TextEditor {
       return;
     }
     for (const path of session.openTabPaths) {
-      if (!this.isSuperuser && typeof path === 'string' && path.startsWith('lib/')) {
-        continue;
-      }
       await this.openFile(path);
     }
     if (session.activeTabPath && this.findTab(session.activeTabPath)) {
@@ -338,7 +335,8 @@ class TextEditor {
   }
 
   getVisibleTopLevelNames() {
-    return this.isSuperuser ? new Set(['code', 'lib']) : new Set(['code']);
+    /* lib is shared read-only for everyone; browsing is allowed, saves are blocked in API/UI. */
+    return new Set(['code', 'lib']);
   }
 
   getDefaultEditableRoot() {
@@ -352,10 +350,7 @@ class TextEditor {
     this.selectedIsDirectory = true;
     this.expandedDirs.add('code');
     await this.loadDirectory('code', { suppressError: true });
-    if (this.isSuperuser) {
-      await this.ensureFolderExists('lib');
-      await this.loadDirectory('lib', { suppressError: true });
-    }
+    await this.loadDirectory('lib', { suppressError: true });
     this.renderFileTree();
   }