- Add client.onclose handler to unregister tools when the MCP server
disconnects (crash or intentional close)
- Replace bare `let disposers` with a shared mutable state object so the
effect disposer and notification handler always reference the current
generation
- Serialize tools/list_changed resyncs with latest-wins coalescing
(syncing + pendingResync flags) to prevent concurrent races
lintianle
f38111e5ca