ci(publish): bump actions/cache v3 → v4

v3 runs on Node.js 20, deprecated by GitHub Actions on 2026-06-02.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: Linuxdazhao

.github/workflows/publish.yml

@@ -24,7 +24,7 @@ jobs:
         toolchain: stable
 
     - name: Cache cargo registry
-      uses: actions/cache@v3
+      uses: actions/cache@v4
       with:
         path: |
           ~/.cargo/registry