Merge the wilm endpoint-monitor and channel-distribution work into main

Six commits from wilm-import: the squashed import, route documentation, the
channel remap onto our tag-and-trunk model, the project map, parallel test
support, and the four smaller review findings.

Merged rather than cherry-picked: the published mirror rewrites hashes, so the
commits do not apply one at a time against our history even though the squashed
diff applies clean.

Scope: product

# Conflicts:
#	docs/PROJECT-MAP.md

.github/workflows/publish-images.yml

@@ -0,0 +1,93 @@
+# Build and publish per-channel container images to GHCR.
+#
+# WHY this exists: pilot dev workstations sit behind an inspecting proxy
+# (Zscaler) that resets npm's many small fetches mid-install, so building the
+# image FROM SOURCE on a pilot box is unreliable. These runners
+# (arc-runner-set) install npm cleanly - the CI `frontend` job already proves
+# it - so we build the image ONCE here and pilots pull the finished image.
+# A single image pull is one resumable HTTPS stream, far more robust through
+# the proxy than hundreds of npm requests.
+#
+# Channels are mapped to how THIS repo actually ships, which is not how the
+# branch this came from ships. Upstream, main is a release branch and dev-be is
+# the trunk. Here main IS the trunk - it runs hundreds of commits past the last
+# release - and releases are tags (ADR-007). Publishing main as :stable would
+# put unreleased work behind a word that promises the opposite, to sites that
+# have no way to know:
+#
+#   tag v*  -> ghcr.io/<owner>/shopdb-flask:stable  (badge off)  the release
+#   main    -> ghcr.io/<owner>/shopdb-flask:edge    (DEV badge)  the trunk
+#
+# The image also carries a short-SHA tag for traceability and rollback.
+#
+# Automatic publishing is OFF until someone confirms the GHCR package exists
+# under this owner and decides who may pull it. Re-enable by uncommenting the
+# push: block below; workflow_dispatch works meanwhile.
+
+name: publish-images
+
+on:
+  # push:
+  #   tags:
+  #     - 'v*'
+  #   branches:
+  #     - main
+  # Manual rebuild/publish of the current ref's channel image.
+  workflow_dispatch:
+
+# One in-flight publish per branch; a newer push supersedes an older one.
+concurrency:
+  group: publish-images-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  build-and-push:
+    runs-on: arc-runner-set
+    permissions:
+      contents: read
+      packages: write
+    steps:
+      - uses: actions/checkout@v5
+
+      # Lowercase the owner: GHCR repository paths must be lowercase, but
+      # github.repository_owner can carry uppercase (e.g. ge-aero is fine, but
+      # this keeps the workflow correct for any owner casing).
+      - name: Resolve image name and channel tag
+        id: meta
+        run: |
+          owner="$(echo '${{ github.repository_owner }}' | tr '[:upper:]' '[:lower:]')"
+          image="ghcr.io/${owner}/shopdb-flask"
+          # A tag is a release, anything else is the trunk. Deliberately not
+          # keyed on the branch name: a release here is a tag, so keying on
+          # "main" would label the trunk stable.
+          if [ "${{ github.ref_type }}" = "tag" ]; then
+            channel="stable"
+          else
+            channel="edge"
+          fi
+          echo "image=${image}" >> "$GITHUB_OUTPUT"
+          echo "channel=${channel}" >> "$GITHUB_OUTPUT"
+          echo "sha=$(git rev-parse --short HEAD)" >> "$GITHUB_OUTPUT"
+
+      - name: Log in to GHCR
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Set up Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Build and push channel image
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          push: true
+          tags: |
+            ${{ steps.meta.outputs.image }}:${{ steps.meta.outputs.channel }}
+            ${{ steps.meta.outputs.image }}:${{ steps.meta.outputs.channel }}-${{ steps.meta.outputs.sha }}
+          # Reuse the channel tag as a cache source/target so subsequent builds
+          # only redo layers that actually changed.
+          cache-from: type=registry,ref=${{ steps.meta.outputs.image }}:${{ steps.meta.outputs.channel }}
+          cache-to: type=inline