Improve question detection, capture stealth, latency; stop tracking model binaries

- Detection: broaden request-starters, handle contractions, allow 1-word '?'
- Audio: PTT pre-roll (no clipped first word), drop Whisper silence hallucinations,
  greedy decoding + domain initial_prompt for faster/cleaner transcription
- AI: cap spoken-answer tokens so replies return at conversational speed
- Overlay: answers persist (no auto-hide); wire Ctrl+Shift+H show/hide toggle
- Screen capture: freeze-frame at hotkey press (immune to focus-blur lockouts),
  hide selector from screen-share (NSWindowSharingNone), higher capture resolution
- Stop tracking models/ and *.zip (large binaries; add to .gitignore)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.gitignore

@@ -102,3 +102,6 @@ dmypy.json
 
 # pyre type checker
 .pyre/models/whisper/model.bin
+
+# Corporate CA bundle (machine-specific, may be sensitive)
+certs/