🔀 Merge chore/remove-toolcache-diagnostics into main

All steps confirmed green in CI ('Found in cache @ /opt/hostedtoolcache/node/
26.8.2/x64', no download). The runner-side force-pull item moves to its own
task, since a changed image under an unchanged tag is still silently ignored.

.gitea/workflows/ci.yml

@@ -63,6 +63,13 @@ jobs:
                 - /data/gitea-pages:/data/gitea-pages
         steps:
             - uses: actions/checkout@v4
+            # Fail fast when the job container is not the baked image: a stale
+            # tag on the runner (`forcePull=false` in its pull log) silently
+            # reintroduces the per-job download. Mirrors the publish job's
+            # NPM_TOKEN assert — cheap, and it names the invariant.
+            - name: Assert the baked tool cache is present
+              run: |
+                  test -f "/opt/hostedtoolcache/node/$(tr -d '[:space:]' < .node-version)/x64.complete"
             - uses: actions/setup-node@v4
               with:
                   node-version-file: .node-version

CONTRIBUTING.md

@@ -102,6 +102,11 @@ Bumping Node is one coordinated change, committed as a unit:
 
 Skipping step 2 fails CI at image pull; skipping step 3 silently reverts to the per-job download.
 
+Two invariants the image must satisfy for the probe to hit, both easy to break:
+
+- **The `x64.complete` marker.** `actions/tool-cache` accepts a cached tool only when `<version>/<arch>.complete` exists next to the directory (`tc.find()` checks it); a plausible-looking `node/<version>/x64/` alone is ignored and the download happens anyway. See the comment in [docker/Dockerfile](./docker/Dockerfile).
+- **Tag freshness.** The tag encodes only the Node version, so a Dockerfile change (like the marker above) produces _new content under an unchanged tag_. `act_runner` skips the pull when a tag of that name already exists locally (`forcePull=false` in the job log), so the runner must either force-pull (`force_pull` under `container:` in its `config.yaml`, if the installed version has it) or have the tag removed on the runner host (`docker rmi gitea.e1nsnull.de/tmu/act-ci:<version>`) after any image change. Symptom of getting this wrong: CI keeps running the previous image while the registry shows the new digest.
+
 ## Publishing workflow
 
 Publishing is CI-only by policy. Local `npm publish` is not supported. The maintainer triggers releases from `main`:

backlog.tasks

@@ -45,7 +45,12 @@ Maintenance:
     ☐ Add a minimal dir-listing webserver to the gitea docker setup for serving landing page (reuse existing reverse proxy)
     ☐ CI writes landing page to a shared volume keyed by project + tag (e.g. `/landing/tiny-pattern-ts/<tag>/`)
     ☐ Browse to `…/tiny-pattern-ts/index.html` in the browser
-☐ Stop Gitea CI re-downloading Node on every job (branch chore/fix-ci)
+✔ Stop Gitea CI re-downloading Node on every job @done
     ✔ Share the warm npm cache with the publish job @done
     ✔ Bake Node into the CI job image (docker/Dockerfile, container.image in ci.yml) @done
-    ☐ Build/push gitea.e1nsnull.de/tmu/act-ci:26.8.2 and confirm setup-node skips the download (first run on the branch = acceptance test) @high
+    ✔ Build/push gitea.e1nsnull.de/tmu/act-ci:26.8.2 and confirm setup-node skips the download @done
+    ✔ Write the `<version>/x64.complete` marker — actions/tool-cache ignores a bare directory, so the probe missed and the download continued @done
+    ✔ Log tool-cache state from the job container to find it (temporary, removed once understood) @done
+    ✔ Guard the invariant in CI (`Assert the baked tool cache is present`) @done
+☐ Enable force-pull for the runner so a changed act-ci image is never missed @low
+    → the tag encodes only the Node version, so a Dockerfile change yields new content under an unchanged tag; with `forcePull=false` the runner keeps the old image (see CONTRIBUTING § CI runner image)

docker/Dockerfile

@@ -39,6 +39,13 @@ ARG NODE_VERSION=26.8.2
 # node image: bin/ + lib/ under /usr/local → tool cache: bin/ + lib/ under <ver>/x64.
 COPY --from=nodebase /usr/local /opt/hostedtoolcache/node/${NODE_VERSION}/x64
 
+# actions/tool-cache only accepts a cached tool when the sibling marker file
+# "<version>/<arch>.complete" exists — tc.find() checks it and falls back to
+# downloading otherwise, however complete the directory is. The marker is what
+# tc.cacheDir() writes after *it* installs a tool, so a pre-baked entry has to
+# reproduce it explicitly.
+RUN touch "/opt/hostedtoolcache/node/${NODE_VERSION}/x64.complete"
+
 # Fail the build (not CI) if the overlay or the version arg were wrong.
 # Shell form on purpose: exec form (`RUN [...]`) does not expand ARG values.
 RUN "/opt/hostedtoolcache/node/${NODE_VERSION}/x64/bin/node" --version