Setup OIDC for CodSpeed authentication (#231)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude <[email protected]>

Author: Boshen

.github/workflows/benchmark.yml

@@ -32,6 +32,8 @@ jobs:
   benchmark:
     name: Benchmark
     runs-on: ubuntu-latest
+    permissions:
+      id-token: write # required for OIDC authentication with CodSpeed
     steps:
       - uses: taiki-e/checkout-action@b13d20b7cda4e2f325ef19895128f7ff735c0b3d # v1.3.1
 
@@ -50,4 +52,3 @@ jobs:
         with:
           run: cargo codspeed run
           mode: instrumentation
-          token: ${{ secrets.CODSPEED_TOKEN }}