feat(ecosystem): adopt hub-core dependency and CI pin gate (CORE-WP-0009)

Import slugify_or_default from hub-core, add contract tests, vendor hub-core in
Docker/Forgejo CI, document metadata isolation and pagination deferral, and
align INTENT/SCOPE with three-repo stack.

.forgejo/workflows/ci-smoke.yaml

@@ -1,5 +1,4 @@
-# Canonical CI smoke template (tier 1 routing drill).
-# Copy to: .forgejo/workflows/ci-smoke.yaml in consumer repos.
+# CI smoke with hub-core sibling vendored for path dependency resolution.
 name: CI Smoke
 
 on:
@@ -8,6 +7,9 @@ on:
       - main
   workflow_dispatch:
 
+env:
+  EXTRA_REPOS: "coulomb/hub-core@hub_core_src"
+
 jobs:
   host-smoke:
     runs-on: self-hosted
@@ -20,10 +22,30 @@ jobs:
           echo "runner=${RUNNER_NAME:-unknown}"
           uname -a
 
-  container-smoke:
-    runs-on: ubuntu-latest
+  pytest-smoke:
+    runs-on: self-hosted
     steps:
-      - name: Routing probe (container label)
+      - name: Test with vendored hub-core
         run: |
           set -eu
-          echo "container-smoke ok for ${GITHUB_REPOSITORY:-unknown}"
+          REF="${GITHUB_SHA:-main}"
+          SHORT="${REF:0:7}"
+          ROOT="${HOME}/ci-core-hub-${SHORT}"
+          rm -rf "${ROOT}"
+          mkdir -p "${ROOT}"
+          wget -qO /tmp/core-hub.tar.gz \
+            "https://forgejo.coulomb.social/${GITHUB_REPOSITORY}/archive/${SHORT}.tar.gz"
+          tar xzf /tmp/core-hub.tar.gz -C "${ROOT}" --strip-components=1
+          wget -qO /tmp/hub-core.tar.gz \
+            "https://forgejo.coulomb.social/coulomb/hub-core/archive/main.tar.gz"
+          mkdir -p "${ROOT}/../hub-core"
+          tar xzf /tmp/hub-core.tar.gz -C "${ROOT}/../hub-core" --strip-components=1
+          cd "${ROOT}"
+          if ! command -v uv >/dev/null 2>&1; then
+            pip install --user uv
+            export PATH="${HOME}/.local/bin:${PATH}"
+          fi
+          uv sync --extra dev
+          uv run python -c "import hub_core; assert hub_core.__version__ >= '0.2.0', hub_core.__version__"
+          uv run python -m pytest -q
+          echo "core-hub pytest smoke ok with hub-core @ ${SHORT}"