fix(ci): use placeholder API key to pass claude-code-action validation

claude-code-action validates that anthropic_api_key is non-empty before
running. CLIProxy ignores this value and uses ANTHROPIC_AUTH_TOKEN for
actual authentication.

.github/workflows/ai-review.yml

@@ -70,7 +70,7 @@ jobs:
       - name: PR Review
         uses: anthropics/claude-code-action@v1
         with:
-          anthropic_api_key: ""
+          anthropic_api_key: ccs-internal-managed
           github_token: ${{ steps.app-token.outputs.token }}
           track_progress: true
           prompt: |