* fix(workspaces): stop archived workspace subscriptions
Workspace mutations were persisted globally but projected only through the initiating session, leaving other sessions' Git observers alive after archive. Publish mutations from the shared registry so every session releases its local observer and receives exactly one update.
* fix(workspaces): serialize workspace mutation observers
* fix(workspaces): finish mutation cleanup
Queued workspace mutations now stop at the session cleanup boundary and remove any observer created across an asynchronous cleanup race. Project removal can still enrich an earlier removal delta for legacy clients.
* fix(workspaces): honor global mutation boundaries
Serialize project and workspace lifecycle notifications per session, keep filtered subscriptions from owning unrelated Git observers, and broadcast final project removals to every session that saw the project. Update strict Session harnesses for the registry subscriptions.
* fix(workspaces): preserve initial agent status
Carry initial-agent intent through global workspace mutations and publish the optimistic running status until the agent contribution takes over. This removes the invalid transient Done state exposed by global subscriptions.
