b0d98d9e2b
- Offloaded slow LSP diagnostics to a deferred channel in the `write` tool to prevent blocking agent execution for the full 3-second poll window. - Abstracted deferred diagnostic logic into a reusable `DeferredDiagnostics` class to standardize tracking and deduplication across tools. - Updated `WriteTool` to support `beginDeferredDiagnosticsForPath` callbacks, surfacing diagnostics as an aside instead of stalling the tool result. - Added a regression test validating that `write` completes immediately while diagnostics arrive asynchronously.