QconnectApp now holds the shared QconnectRemoteSyncState accumulator behind
its own Mutex, disjoint from `state` (the two are never co-locked). The Tauri
adapter still builds the Arc and passes the SAME clone to its event sink /
service loop and into new(), so there is exactly one lock backing the
session/liveness/renderer paths -- the app simply gains a handle to it via
sync_handle(). Pure wiring, byte-identical locking, no logic moved. Prepares
slices 2+4.4/5 to relocate the session-apply + watchdog logic into qconnect-app.
cc
vicrodh
7b143c2738