[michaelm-afk]

Offer Audio Sync Fix 1.0.1 through the existing USA/EU1/EU2/Japan regional catalogs. This updates the existing PR instead of opening a duplicate and merges current master into its branch without rewriting the earlier commits.

Title-owned changes

• One shared declaration and activation plugin, using psxrecomp's public host policy.
• Fresh profiles enable Audio Sync with 70 ms default/Recommended. Preserve existing enabled state and absolute target_ms values.
• Declare 20–180 ms in 5 ms steps, optional diagnostics (OFF by default), and next-game-start semantics. OFF restores the configured fallback, normally180 ms.
• Read only committed mod options at activation and pass the validated absolute target to the engine. No private runtime overlay or engine/UI file patches.
• Shared regional catalog staging retains existing regional packages. Quick Mods uses the normal saved feature state. HQ SPU, game timing and other mods are unchanged.
• Short English user documentation in docs/regional/audio-sync.md.

Dependencies / merge order

1. Preserve audio continuity and expose a next-session buffer target RetroPortingToolKit/psxrecomp#781 — continuity/click correction, configurable target API and diagnostics (follows already-merged engine #769).
2. Expose the saved Audio Sync buffer target with a shared slider RetroPortingToolKit/recomp-ui#122 — shared slider through the existing provider.
3. This title integration, with maintainer-selected accepted public framework pins.

This PR remains draft until those framework changes are accepted and official pins are selected. It does not pin unmerged fork commits or change the USA release files. The new API is required to compile the updated title plugin; the old engine pin alone is insufficient.

Validation and limits

• New current-master engine and paired UI build successfully on Windows Clang Release.
• Title activation test passes default70, saved target, range validation, next-session consumption and OFF fallback.
• Real ModPackageManager persistence test passes fresh70, existing80 retained, upper180 and reset70 retained.
• Shared regional catalog staging test passes. Tests are committed and registered in CMake.
• Earlier official-source USA/EU1/EU2/Japan build/start checks and owner listening acceptance are historical evidence for the preceding implementation. No new all-region gameplay build or campaign run is claimed for this API update.
• The owner confirmed click-free playback and stable70 ms in tested personal EU1 sections. It is not universally qualified. Lower values can stutter/drop out;20 ms was unstable. Physical Windows/HDMI/eARC/speaker latency has not been measured.

Source only, developed with AI assistance. No RA, controller preferences, private paths, game assets, cards, reports, caches, binaries, interpolation or unrelated experiments.