The 9.8k-line collaboration runtime was welded to the desktop GUI
(WidgetHostNative + winit EventLoopProxy), so the web daemon and future
satellite hosts could not run sessions. Split the host coupling behind a
CollabHost trait + wake notifier closure, then move the runtime, JWKS
fetcher, and tests into the new leaf crate op-collab-host:
- CollabHost (CollaborationEditorHost + dirty/id-namespace hooks) with a
HeadlessCollabHost for daemon and test use; the WidgetHostNative impl
lives behind op-host-native's gl-host feature
- async work reaches sync relay/JWKS code through an injected
BlockingExecutor (process-global OnceLock) instead of depending on
op-host-services, keeping the crate graph acyclic
- desktop keeps a thin shim (type alias + wake closure); call sequence
and test assertions unchanged, 154 runtime tests moved as-is
89151683b0