update SYNC.md — fullscreen fix pushed

SYNC.md

@@ -39,6 +39,7 @@ If a plugin crashes → only Helper dies → Ableton survives → UI shows "Relo
 - ❌ `MSG_NOSIGNAL` (doesn't exist on macOS)
 - ❌ Native title bar close button on Helper window (macOS won't deliver clicks to accessory process)
 - ❌ `activateIgnoringOtherApps` (steals focus from Ableton)
+- ❌ `NSFloatingWindowLevel` (level 3) — not high enough for fullscreen apps
 
 ## What's New
 - ✅ Out-of-process via shared memory + semaphores + Unix socket
@@ -47,11 +48,14 @@ If a plugin crashes → only Helper dies → Ableton survives → UI shows "Relo
 - ✅ Toggle GUI via button in PluginBridge panel (Open GUI / Close GUI)
 - ✅ Plugin list from filesystem (no binary loading until user selects)
 - ✅ Native pthread priority for audio thread
-- ✅ `NSApplicationActivationPolicyAccessory` for helper (no Dock, no focus steal)
-- ✅ Policy set in main.cpp initialise() BEFORE any windows created
+- ✅ `NSApplicationActivationPolicyAccessory` in main.cpp (no Dock, no Cmd+Tab)
+- ✅ `NSWindowCollectionBehavior` = canJoinAllSpaces | fullScreenAuxiliary
+- ✅ Window level = 25 (NSStatusWindowLevel) — above fullscreen apps
 
 ## Status
-**Last push:** 2026-05-16 — Fixed GUI opening as separate app. Root cause: activation policy was only set on the window (showAsFloatingPanel) but not on the NSApplication itself. Fix: added `setActivationPolicy:1` (Accessory) as first line in `initialise()` in main.cpp.
+**Last push:** 2026-05-16 — Fixed GUI not appearing over fullscreen Ableton.
+- Root cause: NSFloatingWindowLevel (3) is below fullscreen app level. Window also lacked collection behavior flags to join fullscreen Spaces.
+- Fix: Set `canJoinAllSpaces` (1<<0) + `fullScreenAuxiliary` (1<<8) on the window. Raised level from 3 → 25 (NSStatusWindowLevel).
 **Build:** Needs test
-**Test:** Pull, build, load in Ableton → Open GUI → confirm NO Dock icon, NO Cmd+Tab, window floats over Ableton without switching apps.
+**Test:** Pull, build, load in Ableton FULLSCREEN → Open GUI → confirm plugin window appears OVER fullscreen Ableton (same Space, no desktop switch).
 **Next:** Sprint 3 — MCP param control from Claude Code (curl tests)