ci(fix[docs]): Pin pnpm 11.11.0

why: The moving pnpm 11 range began resolving to 11.12.0, whose bootstrap
self-update crashes in action-setup before the documentation build starts.
The previous docs runs proved 11.11.0 against the committed lockfile.

what:
- Pin the docs workflow to the last known-good pnpm 11 release.

Author: tony

.github/workflows/docs.yml

@@ -67,7 +67,7 @@ jobs:
         if: env.BUILD_DOCS == 'true'
         uses: pnpm/action-setup@v6
         with:
-          version: 11
+          version: 11.11.0
           run_install: false
 
       - name: Install dependencies