Add local-mode workspace, ZIP import/export, and richer pin/ADC/serial sims

Boot:
- Editor now picks local vs server mode based on URL flag, sign-in
  state, and a stale local-mode flag. Signed-in users are no longer
  bounced to IndexedDB if they had previously clicked "Use locally".

Local mode:
- New LocalWorkspaceClient (src/static/local-workspace.js) with
  pluggable IndexedDB and File System Access backends. Picked folder
  handles persist across reloads with a Reconnect button when the
  permission lapses.
- Static-only host: scripts/serve_static_editor.py serves src/static/
  with COOP/COEP so SharedArrayBuffer-backed sims keep working.
- Bundled MicroPython stubs ship under src/static/bundled-lib/ for
  static hosting; FastAPI also exposes them at /api/public/lib-bundle.

Workspace import / export:
- Zero-dep ZIP encoder + reader (STORE + DEFLATE via
  DecompressionStream). Export/Import buttons in the workspace badge
  work in both local and server modes; imports are confined to code/.

Pin / ADC / Serial simulation:
- machine.py grows ADC, UART, expanded Pin, and PWM mocks, all driven
  by SharedArrayBuffer when cross-origin isolated and falling back to
  postMessage + [pin-out] stdout markers otherwise — pins, ADC slider,
  and serial input now keep working over plain HTTP / LAN-IP origins.
- NeoPixel pins are claimed via a [pin-claim] marker and dropped from
  the Pins panel so the data line doesn't flicker per write().
- New demos: adc_slider_demo.py, pin_demo.py, serial_demo.py.

Lib layout:
- Single source of truth at repo lib/; workspace/lib/ caching layer
  removed and the directory deleted. Filesystem service reads stubs
  directly from PROJECT_ROOT/lib.

UI:
- Home page slimmed to "Sign in" + "Use locally" with optional editor
  / manage-users links. Admin user/invite UI moved to /users.
- Workspace badge gains storage indicator, Folder…/Reconnect, Export,
  Import, and Exit controls.
- Mobile-friendly tweaks: safer-area padding, larger touch targets,
  iOS-zoom-proof serial input, file-tree highlight fix.

Tests:
- test_auth.py patches PROJECT_ROOT for the lib-shared test so the
  repo-root lib refactor stays green. test_api.py asserts the new
  "LED Editor" branding.

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

README.md

@@ -90,17 +90,22 @@ Admins can open another user's workspace from the home page user management pane
 
 The home page can store the API key in `sessionStorage` when you are not using cookie login, or use `?api_key=` on `/editor`.
 
+**Local mode (no login)** — Click *Use locally* on the home page (or open `/editor?local=1`) to run the editor without any FastAPI auth. The boot-time auth probe is skipped when local mode is active, so this works even on a host that has `AUTH_ENABLED=true`. Files default to the browser's **IndexedDB**; inside the editor the workspace badge has a **Folder…** button that opens `window.showDirectoryPicker()` so you can save straight to any folder on disk (Chromium-only — Firefox/Safari stay on IndexedDB). The picked directory handle is persisted across reloads in IndexedDB; if browser permission lapses a *Reconnect* button reappears in the badge. Nothing is sent to the server for file reads/writes. The MicroPython stubs are loaded from **`/static/bundled-lib/*.py`** (files under `src/static/bundled-lib/` in the repo) so a plain static file server is enough; if those requests fail, the app falls back to `GET /api/public/lib-bundle` when FastAPI is available. For static-only hosting, run `python scripts/serve_static_editor.py` from the repo root — it serves `src/static/` with the same `/static/…` URLs the HTML expects (it strips the `/static` prefix when resolving files), rewrites `/editor` → `index.html`, and sends the same COOP/COEP headers as the full app so **ADC sliders, pin toggles, and serial I/O** keep using `SharedArrayBuffer` on mobile Safari and Chrome where supported. An *Exit* button in the editor's workspace badge clears the local-mode flag (your IndexedDB files stay until you wipe browser storage).
+
 ## Layout
 
 - `src/` — FastAPI app and static UI (`src/static/`)
-- `lib/` — bundled MicroPython stubs (copied into `WORKSPACE_ROOT/lib` when missing; read-only via API)
-- `workspace/` — default `WORKSPACE_ROOT`: `code/` samples (editable); runtime `lib/` is filled from `lib/` above
+- `lib/` — bundled MicroPython stubs, served read-only as `lib/` in the editor and merged into Pyodide at run time (single source of truth)
+- `workspace/` — default `WORKSPACE_ROOT`: `code/` samples and per-user folders (editable); the editor surfaces the repo `lib/` alongside it without copying anything to disk
 
 ## ESP32 / NeoPixel mock
 
 The browser runtime ships MicroPython-style stubs in repo `lib/` (they appear as `lib/` in the editor and are read-only via the APIs):
 
-- `machine.Pin`, `machine.freq()`, `machine.unique_id()`, `machine.reset()` (no-op here)
+- `machine.Pin` — `value/on/off/toggle/high/low/init/__call__/irq` plus a live "Pins" panel: OUT pins show an indicator, IN pins expose a clickable toggle button (its value is what `Pin.value()` returns), `irq()` fires on rising / falling edges as you click
+- `machine.PWM` — `freq()` / `duty()` / `duty_u16()` / `duty_ns()` with a duty-cycle bar in the Pins panel
+- `machine.ADC` — backed by a live slider in the editor UI (one slider per pin, `read_u16()` returns 0..65535)
+- `machine.UART` — opens a Serial Monitor pane; `write()` text appears there, what you type is delivered via `read()` / `readline()`
 - `neopixel.NeoPixel`
 - `utime` — `ticks_ms`, `ticks_diff`, `ticks_add`, `sleep_ms`, `sleep_us`, `sleep`
 - `micropython.const` — no-op helper for ported constant declarations