ci: log in to the registry with the docker CLI, not docker/login-action

build-ml failed at the login step twice on a7e626a, five seconds in, with
MODULE_NOT_FOUND on the action's own dist/index.js. Not the token — the
secret resolved to *** and the action never ran far enough to use it.

The cause is a race in act_runner's shared action cache, not corruption.
A remote action is cached at one /root/.cache/act/<hash> per runner, and
build-web, build-ml and build-agent all start in the same second and all
want docker/login-action@v3. One job re-clones that directory — emptying
and repopulating it — while another walks it to copy into its container,
and the walker lstat()s a file that just vanished. The two failures named
DIFFERENT missing files, eslint.config.mjs then jest.config.ts, which is
what rules out a bad cache entry and points at the race: a dangling entry
would name the same file every time.

Re-running does not help, because the re-run starts the three jobs
simultaneously again. It reproduced immediately.

Dropping the action removes FC from that race for this step. Logging in is
one command, the docker CLI is already in the CI image per
ci-requirements.md, and the same reasoning as family rule 5 applies: a
marketplace action buys nothing when the tool is baked into the image the
workflow already selected. Password on stdin, never as an argument — an
argument lands in the process table and draws docker's own deprecation
warning.

This narrows the exposure rather than closing it. All three jobs also
share docker/build-push-action@v5 and can race on it the same way; that
one has not lost yet, and replacing it means hand-rolling buildx
invocation including the build-args and provenance handling, which is a
bigger change than this failure justifies. Recorded on #3118.

Live consequence being cleared: fabledcurator-ml:dev was left a commit
behind fabledcurator:dev, which is the stale-pairing trap the trigger
comment on 239b1ed warns about.

.forgejo/workflows/build.yml

@@ -442,12 +442,30 @@ jobs:
             echo "channel=dev" >> "$GITHUB_OUTPUT"
           fi
 
+      # A shell step, not docker/login-action@v3, because the action's shared
+      # cache races itself (#3118). act_runner caches a remote action under one
+      # /root/.cache/act/<hash> per runner, and build-web, build-ml and
+      # build-agent all start in the same second and all want this same action.
+      # One job re-clones the directory — which empties and repopulates it —
+      # while another is walking it to copy into its container, and the walker
+      # lstat()s a file that has just vanished. It failed twice on 2026-08-27,
+      # naming a DIFFERENT missing file each time (`eslint.config.mjs`, then
+      # `jest.config.ts`), which is what rules out a corrupt cache and points at
+      # a race. The loser dies with MODULE_NOT_FOUND on dist/index.js before the
+      # action runs at all, so the secret is never even reached.
+      #
+      # Nothing is lost by dropping it: logging in is one command, the docker
+      # CLI is already in the CI image (ci-requirements.md), and the same
+      # reasoning as family rule 5 applies — a marketplace action buys nothing
+      # when the tool is baked into the image the workflow already selected.
+      #
+      # Password on stdin, never as an argument: an argument lands in the
+      # process table and draws docker's own deprecation warning.
       - name: Login to Forgejo registry
-        uses: docker/login-action@v3
+        env:
-        with:
+          TOKEN: ${{ secrets.RELEASE_TOKEN }}
-          registry: git.fabledsword.com
+          ACTOR: ${{ github.actor }}
-          username: ${{ github.actor }}
+        run: echo "$TOKEN" | docker login git.fabledsword.com -u "$ACTOR" --password-stdin
-          password: ${{ secrets.RELEASE_TOKEN }}
 
       - name: Build and push web image
         uses: docker/build-push-action@v5
@@ -490,12 +508,13 @@ jobs:
             echo "tags=git.fabledsword.com/bvandeusen/fabledcurator-ml:dev" >> "$GITHUB_OUTPUT"
           fi
 
+      # Shell step rather than docker/login-action — see build-web's note on
+      # the shared action-cache race (#3118).
       - name: Login to Forgejo registry
-        uses: docker/login-action@v3
+        env:
-        with:
+          TOKEN: ${{ secrets.RELEASE_TOKEN }}
-          registry: git.fabledsword.com
+          ACTOR: ${{ github.actor }}
-          username: ${{ github.actor }}
+        run: echo "$TOKEN" | docker login git.fabledsword.com -u "$ACTOR" --password-stdin
-          password: ${{ secrets.RELEASE_TOKEN }}
 
       - name: Build and push ml image
         uses: docker/build-push-action@v5
@@ -528,12 +547,13 @@ jobs:
             echo "tags=git.fabledsword.com/bvandeusen/fabledcurator-agent:dev" >> "$GITHUB_OUTPUT"
           fi
 
+      # Shell step rather than docker/login-action — see build-web's note on
+      # the shared action-cache race (#3118).
       - name: Login to Forgejo registry
-        uses: docker/login-action@v3
+        env:
-        with:
+          TOKEN: ${{ secrets.RELEASE_TOKEN }}
-          registry: git.fabledsword.com
+          ACTOR: ${{ github.actor }}
-          username: ${{ github.actor }}
+        run: echo "$TOKEN" | docker login git.fabledsword.com -u "$ACTOR" --password-stdin
-          password: ${{ secrets.RELEASE_TOKEN }}
 
       - name: Build and push agent image
         uses: docker/build-push-action@v5