ci: free disk space at the start of each integration test job

Two failures in the previous run (test-traefik full, test-nginx
simple) ended with the runner reporting "No space left on device"
while flushing its diagnostic log. ubuntu-latest starts with ~14 GB
free; downloading the full image artifact (5-8 GB), loading it into
docker (decompressed, larger), pulling kind's node image, then
loading the OCI tar into the kind cluster easily exceeds that budget.

Mirror the cleanup already used by `build-arm64`: drop the runner's
preinstalled dotnet / android SDK / ghc / hostedtoolcache to recover
~30 GB. Same step now runs at the top of test-apptainer, test-nginx,
and test-traefik on both amd64 (ubuntu-latest) and arm64
(ubuntu-24.04-arm) matrix entries — the arm runner is at least as
tight as amd64.

Author: claude

.github/workflows/build-and-test.yml

@@ -296,6 +296,16 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
+      - name: Free disk space
+        # ubuntu-latest has ~14 GB free; the full image (5-8 GB) plus kind
+        # node image plus loading the OCI tar into both docker and kind can
+        # exhaust it. The arm runner is even tighter. Same incantation as
+        # `build-arm64`'s "Free disk space" step.
+        run: |
+          sudo rm -rf /usr/share/dotnet /usr/local/lib/android /opt/ghc /opt/hostedtoolcache || true
+          sudo apt-get clean
+          df -h
+
       - name: Download image artifact
         uses: actions/download-artifact@v4
         with:
@@ -530,6 +540,16 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
+      - name: Free disk space
+        # ubuntu-latest has ~14 GB free; the full image (5-8 GB) plus kind
+        # node image plus loading the OCI tar into both docker and kind can
+        # exhaust it. The arm runner is even tighter. Same incantation as
+        # `build-arm64`'s "Free disk space" step.
+        run: |
+          sudo rm -rf /usr/share/dotnet /usr/local/lib/android /opt/ghc /opt/hostedtoolcache || true
+          sudo apt-get clean
+          df -h
+
       - name: Download image artifact
         uses: actions/download-artifact@v4
         with:
@@ -629,6 +649,16 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
+      - name: Free disk space
+        # ubuntu-latest has ~14 GB free; the full image (5-8 GB) plus kind
+        # node image plus loading the OCI tar into both docker and kind can
+        # exhaust it. The arm runner is even tighter. Same incantation as
+        # `build-arm64`'s "Free disk space" step.
+        run: |
+          sudo rm -rf /usr/share/dotnet /usr/local/lib/android /opt/ghc /opt/hostedtoolcache || true
+          sudo apt-get clean
+          df -h
+
       - name: Download image artifact
         uses: actions/download-artifact@v4
         with: