Add constant volume output setting

[Gleek]

• Adds a new Output setting for Constant volume, off by default
• Compensates Thock playback gain against the current system output volume
• Reads output volume from CoreAudio, preferring dB volume and falling back to virtual/scalar volume properties
• Keeps compensation internal to Thock without changing macOS system volume

Fixes #74

[greptile-apps]

Greptile Summary

This PR adds a "Constant volume" setting that compensates Thock's playback gain against the current macOS system output volume, keeping keyboard sounds at a consistent perceived level when the user adjusts system volume. It reads output volume via CoreAudio (preferring dB, falling back to VirtualMainVolume and scalar), stores the preference in UserDefaults, and exposes a toggle in SoundSettingsView.

• AudioDeviceManager grows three new private helpers to read system output volume via kAudioDevicePropertyVolumeDecibels, kAudioHardwareServiceDeviceProperty_VirtualMainVolume, and kAudioDevicePropertyVolumeScalar, called before each sound is scheduled.
• SoundManager caches systemOutputVolume and applies a compensation formula (appVolume / pow(outputVolume, 1.08)) in the real-time render callback, with a maximumGain cap and a small minimumSystemVolume floor to prevent division near zero.
• Settings plumbing follows the existing SettingsEngine / SettingsManager / UserDefaults pattern; the UI toggle is integrated into SoundSettingsView with correct onChange and onReceive sync.

Confidence Score: 3/5

The core settings plumbing and UI are solid, but the volume-reading logic in AudioDeviceManager has a fallback path that can silently return a per-channel (not master) volume value, making the compensation wrong on affected devices. The maximumGain ceiling is also set high enough to cause PCM clipping at moderate-low system volumes.

The per-channel dB fallback in getOutputDecibelVolume returns channel 1's reading instead of the master volume when the main channel lacks dB support — on a device where the user has adjusted audio balance, this feeds a wrong divisor into currentRenderVolume(), producing incorrect gain compensation. Separately, the 100× maximumGain cap allows the compensated scalar to climb well into the clipping zone for typical normalized PCM data at moderate-low system volumes (~20–30%), defeating the feature's goal of clean constant-level output. Both issues are in the two most central new files.

AudioDeviceManager.swift (volume-reading priority and per-channel fallback) and SoundManager.swift (maximumGain ceiling and lockless-read scope).

Important Files Changed

Filename	Overview
Thock/Managers/AudioDeviceManager.swift	Adds CoreAudio volume-reading helpers; per-channel dB fallback (channels 1 & 2) can return non-master volume when audio balance is adjusted, leading to incorrect compensation.
Thock/Managers/SoundManager.swift	Adds system-volume snapshot and compensation formula; maximumGain cap of 100× is well above the clipping threshold for normalized PCM data at moderate-low system volumes.
Thock/Engines/SettingsEngine.swift	Adds getter/setter pair for constantVolumeEnabled with correct notification posting; no issues.
Thock/Managers/SettingsManager.swift	Adds UserDefaults persistence for constantVolumeEnabled with correct default-fallback pattern; no issues.
Thock/Helpers/Localization.swift	Adds constantVolume and constantVolumeSubtitle strings for all supported languages; no issues.
Thock/Views/Settings/SoundSettingsView.swift	Adds toggle row for constant volume with correct onChange and onReceive sync; no issues.

_{Reviews (1): Last reviewed commit: "Add constant volume output setting" | Re-trigger Greptile}

[kamillobinski]

thanks! ill do the cr tomorrow
we back