feat: add notification sound option for corrections

[chernistry]

Summary

Add an optional subtle audio notification when RightLayout performs a correction. This provides immediate feedback that a correction occurred, which is especially important for accessibility — users who cannot easily see the menu bar indicator need an alternative feedback channel.

Why This Matters

• Accessibility: Users with visual impairments need auditory feedback
• Attention: When focused on content (not the menu bar), users may miss visual correction indicators
• Confidence: Audio confirmation helps users trust that the tool is working
• Customization: Power users want to tune their experience

Proposed Implementation

Settings

Add to preferences:

• Correction sound: On / Off (default: Off)
• Sound type: System sound picker (Tink, Pop, Frog, Glass, etc.) or "Custom..."
• Volume: Slider (0-100%, independent of system volume — or tied to system alert volume)

Sound Selection

Built-in options (macOS system sounds):

• Tink — subtle, professional (recommended default when enabled)
• Pop — slightly more noticeable
• Glass — traditional macOS alert
• Frog — playful
• Custom sound file (.aiff or .wav)

Implementation

import AppKit

// Play system sound
NSSound(named: "Tink")?.play()

// Or use AudioServicesPlaySystemSound for even lighter weight
import AudioToolbox
AudioServicesPlaySystemSound(1104) // Tink system sound ID

Where to trigger

File: RightLayout/Sources/Engine/EventMonitor.swift or correction handler

After a successful correction:

1. Check if sound is enabled in preferences
2. Play the selected sound
3. Do NOT play sound if correction was undone (to avoid double-feedback)

Rate limiting

• If multiple corrections happen rapidly (e.g., correcting a sentence), don't play sound for every word
• Debounce: play at most once per 500ms
• Or: play once per correction batch (if multiple words are corrected together)

Settings UI

File: RightLayout/Sources/UI/SettingsView.swift

Add a "Sound" section to preferences:

[ ] Play sound on correction
  Sound: [Tink ▼]
  [Preview]  — button to hear the selected sound

Accessibility Considerations

• Sound should complement, not replace, visual indicators
• Consider VoiceOver announcement as an alternative: "Layout corrected to Russian"
• Respect macOS "Play user interface sound effects" system preference
• Consider haptic feedback on MacBooks with Force Touch trackpad (nice to have)

Test Cases

• Sound plays on correction when enabled
• No sound when disabled
• Sound selection persists across app restarts
• Preview button plays the selected sound
• Rate limiting prevents rapid-fire sounds
• Respects system "Do Not Disturb" / Focus mode
• Custom sound file can be loaded

References

• NSSound documentation
• AudioServicesPlaySystemSound
• macOS system sounds location: /System/Library/Sounds/