Step 263: saveBuffer/saveAllBuffers RPC methods write editBuf to disk with
workspace path resolution and parent dir creation. 12/12 tests.
Step 264: State-based undo/redo via HeadlessUndoStack. Snapshots recorded
automatically before mutations; undo/redo restore AST + editBuf. 12/12 tests.
Step 265: Phase 9e integration tests — save after undo/redo, mixed undo
states across buffers, full open→mutate→diagnose→undo→redo→save. 8/8 tests.
Phase 9e complete: 32/32 tests. Sprint 9 total: 244/244 across 5 phases.
34 MCP tools.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
