Fix BLE disconnect crash and event listener leaks

[makermelissa-piclaw]

Summary

Fixes #377 — BLE disconnect during file write operations throws Modal has not been opened yet. No instance available and, in most cases, prevents the UI from being used again without a page refresh.

Root cause

Two separate bugs in js/workflows/ble.js compound into the reported crash:

Bug 1 — connectionStep() called when no dialog is open

When BLE disconnects mid-file-write (not during the connect flow), the chain is:

gattserverdisconnected event
  → onDisconnected()          (workflow.js)
    → updateConnected(false)   (workflow.js)
      → connectionStep(2)      (ble.js override)
        → _markStepCompleted(2)
          → this.connectDialog.getModal()  ❌ throws

getModal() throws because connectDialog was never opened in this lifecycle — the user was editing a file, not walking the connect wizard. This matches the stack trace in the issue exactly.

Bug 2 — Event listener removal no-ops

switchToDevice() and connectToSerial() attempt to clean up listeners with:

device.removeEventListener('gattserverdisconnected', this.onDisconnected.bind(this));

Every .bind(this) call returns a new function reference, so removeEventListener never matches the previously-added listener. Each reconnect leaks another handler, causing duplicate disconnect callbacks (which makes Bug 1 fire multiple times on a single disconnect).

The same pattern exists for onSerialReceive and the advertisement listener in connectToBluetoothDevice().

Fix

1. Guard connectionStep() in updateConnected() behind connectDialog.isOpen() so step-marking only runs when the dialog actually exists.
2. Store bound handlers in the constructor (_boundOnDisconnected, _boundOnSerialReceive) and reuse the same reference for both addEventListener and removeEventListener.
3. Fix advertisement listener cleanup in connectToBluetoothDevice() the same way (_boundOnAdvertisementReceived), and remove any previous listener before attaching a new one.

Testing

• npx vite build passes cleanly.

• Reproduced the crash signature against the unpatched getModal() path and verified the guard short-circuits it while preserving normal behavior when the dialog is open:

  Scenario	Unpatched	Patched
  Disconnect while connect dialog closed (the bug)	❌ Modal has not been opened yet	✅ Skipped safely
  Normal connect with dialog open	✅ Works	✅ Works

• Hardware end-to-end (file write → disconnect) testing was limited by Linux Chromium watchAdvertisements flakiness; local-only bench review confirms the listener-identity fix, and reviewers on macOS/Windows Chrome can exercise the full flow.

Notes

Only js/workflows/ble.js is modified. No behavior change for connected users or normal flows — only the error path is fixed.