fix: Add setup step to report job to install LLVM tools

The report job wasn't installing llvm and clang packages, causing
llvm-profdata and llvm-cov to not be found. Add quick apt install step.

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

Co-Authored-By: Claude Haiku 4.5 <[email protected]>

Author: cdecker

.github/workflows/coverage-nightly.yaml

@@ -220,6 +220,11 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v4
 
+      - name: Install dependencies
+        run: |
+          sudo apt-get update -qq
+          sudo apt-get install -qq --no-install-recommends -yy llvm clang
+
       - name: Verify LLVM tools are available
         run: |
           echo "Verifying LLVM tools are available..."