🔊 Log tool-cache state in the CI build job

The custom image provably carries /opt/hostedtoolcache/node/26.8.2/x64/bin/node
(ls inside the image confirms the layout, modes and the 150 MB binary), yet
setup-node still downloads. So the miss is runtime-only: either the runner is
not running that image or something shadows the path inside the job container.
This step prints mounts, the tool-cache listing, a direct node -v from the
baked path and the RUNNER_* env, then setup-node runs unchanged.

Temporary: remove once the cause is known.

.gitea/workflows/ci.yml

@@ -63,6 +63,22 @@ jobs:
                 - /data/gitea-pages:/data/gitea-pages
         steps:
             - uses: actions/checkout@v4
+            # TEMPORARY (remove once understood): the image provably carries
+            # the tool-cache entry (verified with `docker run --rm <image> ls
+            # /opt/hostedtoolcache/node/26.8.2/x64/bin`), yet setup-node still
+            # downloads. Print what the job container actually sees at
+            # runtime, mounts first — a mount over /opt/hostedtoolcache would
+            # hide the baked directory from the probe.
+            - name: Tool cache diagnostics
+              run: |
+                  id
+                  grep -E 'hostedtoolcache|workspace|overlay' /proc/mounts || true
+                  ls -la /opt/hostedtoolcache || true
+                  ls -la /opt/hostedtoolcache/node || true
+                  ls -la "/opt/hostedtoolcache/node/$(tr -d '[:space:]' < .node-version)/x64/bin" || true
+                  "/opt/hostedtoolcache/node/$(tr -d '[:space:]' < .node-version)/x64/bin/node" -v || true
+                  env | grep -iE 'RUNNER|TOOL|CACHE' || true
+                  head -2 /etc/os-release
             - uses: actions/setup-node@v4
               with:
                   node-version-file: .node-version