ci: free runner disk before the default-lane build

Three runs died on 'No space left on device' + lld Bus error during the
full workspace test build. Drop preinstalled SDKs (dotnet, Android, ghc,
CodeQL) we never use.

Author: hortovanyi

.github/workflows/ci.yml

@@ -24,6 +24,13 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
+      # The full workspace debug build (all test binaries) overflows the
+      # default runner disk — three runs died on "No space left on device"
+      # with lld Bus errors. Drop the preinstalled SDKs we never use.
+      - name: Free runner disk space
+        run: |
+          sudo rm -rf /usr/share/dotnet /usr/local/lib/android /opt/ghc /opt/hostedtoolcache/CodeQL
+          df -h /
       - uses: dtolnay/rust-toolchain@stable
         with:
           components: clippy