Windows Nebula WebView2 MCQ (glass aesthetic)

[theoriginalcheese]

Summary

• Add a frameless Windows Nebula WebView2 MCQ backend (pywebview) with freeze hardening under Cursor (no on_top / AttachThreadInput from the JS bridge; soft Win32 raise; warm profile; hide-then-exit).
• Glass aesthetic: double-bezel options, OK arm fill, select checks, grain, and Nebula-style wind-drift starfield; tk fallback + optional Edge --app path retained.
• Docs/skill: Windows behaviour table + agent habit updates; merged with latest upstream Confirm UX / CI fixes.

Test plan

• On Windows 11: ASK_QUESTION_WIN_UI=pywebview — MCQ opens frameless, on top, responsive (no freeze)
• Starfield visible behind glass; Enter closes with short fade
• ASK_QUESTION_WIN_UI=tk still works as fallback
• Linux Gtk path unchanged (smoke if available)
• uv run python -m ask_question_mcp.doctor --json reports Windows UI ready

[theoriginalcheese]

Squashed the branch to a single commit on top of current main so the review diff is easier to read (force-push was only to my fork theoriginalcheese/ask-question-mcp, not to this repo).

Windows default UI is frameless Nebula glass WebView2; Edge --app and tk remain fallbacks.