Pin every action to a commit SHA

A tag is a mutable pointer. `actions/checkout@v7` is whatever the
publisher last moved v7 to, so using one is not trusting the version that
was reviewed -- it is trusting every future version, including whatever
is pushed by whoever compromises the publisher's account. That is the
shape of the tj-actions/changed-files compromise: no repository changed a
line, the tags moved underneath them, and the action began dumping runner
memory to the logs.

Each `uses:` now carries the full 40-character SHA with its release in a
trailing comment. Read the comment for the version; the SHA is what runs.
Dependabot already covers github-actions weekly and updates both halves
together, so keeping current costs nothing.

The dataaxiom cleanup action was already pinned -- it is handed
`packages: write` and deletes things, so it was worth doing early -- and
only picks up the trailing-version convention here. Its comment loses the
"rather than a moving major tag" framing, which is no longer what makes
it different from its neighbors now that they are all pinned too.

The two `uses: ./.github/workflows/...` entries are local paths, not
actions: they always resolve within the commit already running and there
is no SHA to pin.

.github/workflows/publish.yml

@@ -76,11 +76,11 @@ jobs:
       version: ${{ steps.v.outputs.version }}
       docker_tag: ${{ steps.v.outputs.docker_tag }}
     steps:
-      - uses: actions/checkout@v7
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
         with:
           ref: ${{ inputs.ref || github.ref }}
           fetch-depth: 0
-      - uses: actions/setup-node@v7
+      - uses: actions/setup-node@820762786026740c76f36085b0efc47a31fe5020 # v7.0.0
         with:
           node-version: 26
       - id: v
@@ -108,18 +108,18 @@ jobs:
           - platform: linux/arm64
             runner: ubuntu-24.04-arm
     steps:
-      - uses: actions/checkout@v7
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
         with:
           ref: ${{ inputs.ref || github.ref }}
-      - uses: docker/setup-buildx-action@v4
-      - uses: docker/login-action@v4
+      - uses: docker/setup-buildx-action@594f3bf4285d9ea8dc53c9a0c9c4092420091003 # v4.4.0
+      - uses: docker/login-action@dbcb813823bdd20940b903addbd779551569679f # v4.6.0
         with:
           registry: ghcr.io
           username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
       - name: Build and push by digest
         id: push
-        uses: docker/build-push-action@v7
+        uses: docker/build-push-action@c3c9e263c25d99ce0380d002d59b67737d91b0dc # v7.4.0
         with:
           context: .
           platforms: ${{ matrix.platform }}
@@ -140,7 +140,7 @@ jobs:
           # `image@sha256:sha256:...` when the reference is rebuilt.
           digest="${{ steps.push.outputs.digest }}"
           touch "/tmp/digests/${digest#sha256:}"
-      - uses: actions/upload-artifact@v7
+      - uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
         with:
           # One artifact per platform; the merge job globs them back together.
           name: digest-${{ strategy.job-index }}
@@ -157,13 +157,13 @@ jobs:
       contents: read
       packages: write
     steps:
-      - uses: actions/download-artifact@v8
+      - uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c # v8.0.1
         with:
           path: /tmp/digests
           pattern: digest-*
           merge-multiple: true
-      - uses: docker/setup-buildx-action@v4
-      - uses: docker/login-action@v4
+      - uses: docker/setup-buildx-action@594f3bf4285d9ea8dc53c9a0c9c4092420091003 # v4.4.0
+      - uses: docker/login-action@dbcb813823bdd20940b903addbd779551569679f # v4.6.0
         with:
           registry: ghcr.io
           username: ${{ github.actor }}