feat(ui): floating glowing dictation overlay

[jatinkrmalik]

Summary

Adds a SuperWhisper-style floating on-screen indicator so users can see that the mic is hot without staring at the tray icon.

• Glowing orb at the bottom-center while recognition is LISTENING (green pulse) or PROCESSING (amber, quieter)
• Passive window: no keyboard focus, skip taskbar/pager, click-through input region
• Soft optional GtkLayerShell on Wayland; plain always-on-top GTK window everywhere else (no new hard dependency)
• Settings → General → Show Dictation Overlay (ui.show_overlay, default on)

Wired through the same RecognitionState callbacks as the tray icon (toggle and push-to-talk).

How to try it locally

git fetch origin feature/dictation-overlay
git checkout feature/dictation-overlay
pip install -e ".[dev]"   # or ./install.sh --dev
vocalinux --debug
# or: PYTHONPATH=src python -m vocalinux.main --debug

1. Start dictation with your hotkey (toggle or hold push-to-talk).
2. You should see a green glowing orb near the bottom of the screen while listening, then amber while processing, and it should disappear when idle.
3. Tray icon still goes green/orange as before.
4. Turn it off under Settings → General → Show Dictation Overlay if you prefer tray-only.

Test plan

• pytest tests/test_dictation_overlay.py (state → show/hide, disabled config, non-focus flags, soft layer-shell)
• Related tray/config/settings tests still pass
• Manual: hotkey start → overlay appears; stop → hides
• Manual: disable overlay in Settings while listening → hides immediately
• Manual: X11 and/or Wayland session if available

Screenshots (overlay)

Floating indicator while recognition is active:

Listening (green)	Processing (amber)

[codecov]

Codecov Report

❌ Patch coverage is 92.61745% with 22 lines in your changes missing coverage. Please review.
✅ Project coverage is 84.82%. Comparing base (0a7acae) to head (392dd77).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/vocalinux/ui/dictation_overlay.py	92.41%	18 Missing and 3 partials ⚠️
src/vocalinux/ui/tray_indicator.py	94.11%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #516      +/-   ##
==========================================
+ Coverage   84.39%   84.82%   +0.42%     
==========================================
  Files          32       33       +1     
  Lines        5672     5970     +298     
  Branches      915      950      +35     
==========================================
+ Hits         4787     5064     +277     
- Misses        687      705      +18     
- Partials      198      201       +3     

Files with missing lines	Coverage Δ
src/vocalinux/ui/config_manager.py	98.73% <100.00%> (+0.03%)	⬆️
src/vocalinux/ui/tray_indicator.py	84.61% <94.11%> (+0.78%)	⬆️
src/vocalinux/ui/dictation_overlay.py	92.41% <92.41%> (ø)

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