Windows UI Automation exposes Buzz controls without usable window geometry or focus

## Summary

Buzz renders correctly and its WebView controls appear in the Windows UI Automation tree, but the top-level window is reported with unusable 15 by 15 geometry and interactive descendants cannot be invoked by geometry-backed accessibility clicks.

## Reproduction

1. Install and start Buzz Desktop 0.5.3 on Windows 11.
2. Inspect the native window through Windows UI Automation.
3. Confirm that named buttons, channels, dialogs, and message text are present in the accessibility tree.
4. Attempt to invoke a named button through a geometry-backed UI Automation click.
5. Open Search and compare the visibly focused search input with the focused element reported by UI Automation.

## Expected

The top-level window and descendants expose usable bounding rectangles, accessible buttons can be invoked, and UI Automation focus follows the visibly focused search input.

## Actual

The window is reported as 15 by 15 even while visibly maximized. Geometry-backed clicks fail because interactive descendants have no usable input geometry, and focus remains on the root web document while the search input is visibly focused. Keyboard shortcuts and text extraction still work.

## Environment

- buzz: `desktop-v0.5.3 release build`
- os: `Windows 11`
- webview: `Microsoft Edge WebView2`

## Impact

Windows accessibility tooling and deterministic UI automation can read Buzz but cannot reliably operate it, which weakens screen-reader confidence, enterprise testability, and unattended quality-control coverage.

## Workaround

Use global keyboard shortcuts and keyboard navigation where available; avoid coordinate or element-index clicks until the native window and WebView bounding geometry are exposed correctly.

## Disclosure check

- Client data: no
- Credentials or private hosts: no
- Reproduction contains only synthetic or product-level evidence