Phase 6 + GUI: Distribution and in-game audio mixer

Added:
- GUI/AudioMixerGUI.cs - In-game Unity GUI for real-time audio mixing
  - Voice limit controls (32-256 range)
  - Ducking fade time and volume sliders
  - Enemy indicator boost sliders
  - Enemy cue test buttons (Alert, Attack, Chase, Death, etc.)
  - Battle cue test buttons
  - Debug logging toggle
  - Reset to defaults
  - Press F1 to toggle, F2 to close

Updated:
- Plugin.cs - Initializes AudioMixerGUI on startup
- HomuraHimeAudioMod.csproj - Removed failed ImGui deps, using Unity native GUI

Added:
- docs/EXISTING_TOOLS.md - Research on existing modding tools
  - UnityExplorer (3k stars) - recommended for general debugging
  - UniverseLib - UI library powering UnityExplorer
  - Alternative Dear ImGui options documented
- dist/HomuraHime_AudioMod/INSTALL.md - Distribution package README

Recommendation: Use BOTH UnityExplorer (F5) for general debugging + our AudioMixerGUI (F1) for audio-specific controls

dist/HomuraHime_AudioMod/INSTALL.md

@@ -0,0 +1,127 @@
+# HomuraHime Audio Mod - Installation Guide
+
+## Quick Install
+
+### Prerequisites
+- HomuraHime on Steam
+- BepInEx 5.x
+
+### Steps
+
+1. **Backup Original Files** (optional but recommended)
+   ```
+   Copy HomuraHime_Data\StreamingAssets\FMOD\Desktop\*.bank to backup folder
+   ```
+
+2. **Install BepInEx** (if not already installed)
+   - Download BepInEx 5.x from: https://github.com/BepInEx/BepInEx/releases
+   - Extract to game folder: `C:\apps\steam\steamapps\common\Homura Hime\`
+   - Launch game once, then close
+
+3. **Copy Mod Files**
+   ```
+   Copy BepInEx\plugins\HomuraHimeAudioMod.dll
+   To:   C:\apps\steam\steamapps\common\Homura Hime\BepInEx\plugins\
+   ```
+
+4. **Launch Game**
+   ```
+   Start HomuraHime via Steam
+   Check BepInEx\LogOutput.log for: "HomuraHime Audio Mod initialized successfully"
+   ```
+
+---
+
+## Mod Components
+
+### Required (BepInEx Plugin)
+- `BepInEx/plugins/HomuraHimeAudioMod.dll` - Main mod DLL
+
+### Optional (FMOD Banks)
+- `FMOD_banks/Desktop/*.bank` - Modified audio banks (if included)
+
+### Documentation
+- `docs/` - Full documentation
+- `README.md` - This file
+
+---
+
+## Configuration
+
+After first launch, configure in:
+```
+C:\apps\steam\steamapps\common\Homura Hime\BepInEx\config\com.homurahime.audiomod.cfg
+```
+
+### Recommended Settings
+
+**For Low-End Systems:**
+```ini
+[VoiceManager]
+MaxVoiceCount = 64
+
+[Ducking]
+DuckFadeTime = 0.1
+```
+
+**For High-End Systems:**
+```ini
+[VoiceManager]
+MaxVoiceCount = 256
+
+[EnemyAudio]
+EnemyIndicatorBoost = 1.5
+AlertSoundBoost = 1.6
+AttackSoundBoost = 1.4
+```
+
+---
+
+## Troubleshooting
+
+### Mod Not Loading
+1. Check `BepInEx\LogOutput.log`
+2. Ensure DLL is in `BepInEx\plugins\` (not a subfolder)
+3. Verify .NET Framework 4.8 is installed
+
+### Audio Glitches Persist
+1. Reduce `MaxVoiceCount` to 64
+2. Increase `DuckFadeTime` to 0.1
+3. Disable FMOD banks modification if using
+
+### Game Crashes
+1. Disable mod temporarily
+2. Test with default settings
+3. Check for conflicting mods
+
+---
+
+## Uninstall
+
+1. Delete `BepInEx\plugins\HomuraHimeAudioMod.dll`
+2. Restore original FMOD banks from backup (if modified)
+3. Delete config: `BepInEx\config\com.homurahime.audiomod.cfg`
+
+---
+
+## Version History
+
+### v1.0.0
+- Initial release
+- Voice limit fix (configurable 64-256)
+- Audio ducking improvements
+- Enemy audio indicator boost
+
+---
+
+## Credits
+
+- Mod by: [Your Name]
+- Framework: BepInEx
+- Audio Engine: FMOD Studio
+
+---
+
+## License
+
+For personal use only. Please respect game copyright.