VR-first UI: floating windows, left-hand card, keyboard, and dictation

[kburzota]

Summary

Stacked on #285 (merge that first; this PR’s unique commits sit on top of the WebXR base).

Makes every office window usable inside the headset without a physical keyboard:

• Open windows are mirrored onto a floating panel you click with the controller rays (iframe windows still leave VR)
• A palette-style action card on the left controller (Find, Menu, boards, Keyboard, Dictate, Exit VR, …)
• Full virtual keyboard when a text field is focused; terminal “Type…” opens it instead of exiting VR
• Hold A to dictate (browser speech recognition, or Whisper via POST /api/transcribe when OPENAI_API_KEY is set)
• Point at a wall card and pull the trigger to open it in front of you; right grip takes an issue note

Test plan

• npm run typecheck
• npm test (613 pass)
• npm run build
• Headless canvas preview of keyboard + left-hand card (scripts/xr-ui-preview.png)
• On a Quest: Enter VR, open Settings from the left-hand card, click around, type with the keyboard
• Hold A to dictate into a prompt / terminal (with and without browser speech recognition)
• Trigger on an issues / PR sticky note opens a floating window; right grip takes an issue note
• Open a terminal panel, use Type…, confirm VR stays on

[kburzota]

Opened against the wrong repo; moved to my fork.

[schnepg1]

very nice, I had the idea already, too!