补充 OPFS session persistence release gate 文档

wasm-port/README.md

@@ -130,5 +130,8 @@ Directory intent:
 - `tests/fixtures/`: stable simulation inputs shared by native and browser tests.
 - `build/` and `dist/`: generated outputs only; never hand-edited.
 
+Project-level OPFS/session persistence and release-gate handoff is documented in
+`docs/opfs-session-persistence.md`.
+
 The presence of this directory means the port is managed independently of the
 native LinuxCNC tree even though LinuxCNC remains the semantic source of truth.