refactor: remove plugin file-lock sdk

docs/plugins/sdk-migration.md

@@ -449,7 +449,6 @@ releases.
     | Bounded async task concurrency | `openclaw/plugin-sdk/concurrency-runtime` |
     | Numeric coercion | `openclaw/plugin-sdk/number-runtime` |
     | Process-local async lock | `openclaw/plugin-sdk/async-lock-runtime` |
-    | File locks | `openclaw/plugin-sdk/file-lock` |
 
     Bundled plugins are scanner-guarded against `infra-runtime`, so repo code
     cannot regress to the broad barrel.

docs/plugins/sdk-subpaths.md

@@ -258,7 +258,6 @@ focused channel/runtime subpaths, `config-contracts`, `string-coerce-runtime`,
     | `plugin-sdk/model-session-runtime` | Model/session override helpers such as `applyModelOverrideToSessionEntry` and `resolveAgentMaxConcurrent` |
     | `plugin-sdk/talk-config-runtime` | Talk provider config resolution helpers |
     | `plugin-sdk/json-store` | Small JSON state read/write helpers |
-    | `plugin-sdk/file-lock` | Re-entrant file-lock helpers |
     | `plugin-sdk/persistent-dedupe` | SQLite-backed dedupe cache helpers |
     | `plugin-sdk/acp-runtime` | ACP runtime/session and reply-dispatch helpers |
     | `plugin-sdk/acp-runtime-backend` | Lightweight ACP backend registration and reply-dispatch helpers for startup-loaded plugins |