REUSE-WP-0019-T03: add Forgejo Actions workflows (part 2 of prior commit)

The .forgejo/workflows/ files and doc updates described in 4862ed6 didn't
actually get staged there (git add silently skipped them after an earlier
pathspec miss on the already-deleted .gitea file) -- committing them now.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

.forgejo/workflows/ci.yml

@@ -0,0 +1,77 @@
+# Ported from .gitea/workflows/ci.yml (REUSE-WP-0019-T03). No actions/checkout
+# on this runner substrate (railiance-enablement/docs/forgejo-actions-workflow-templates.md)
+# -- ubuntu-latest maps to docker://node:20-bookworm, no Python preinstalled,
+# so use archive checkout + apt.
+name: ci
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+  workflow_dispatch:
+
+jobs:
+  validate-registry:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Archive checkout
+        run: |
+          set -eu
+          REF="${GITHUB_SHA:-main}"
+          SHORT="${REF:0:7}"
+          mkdir -p /tmp/repo
+          wget -qO /tmp/repo.tar.gz "https://forgejo.coulomb.social/${GITHUB_REPOSITORY}/archive/${SHORT}.tar.gz"
+          tar xzf /tmp/repo.tar.gz -C /tmp/repo --strip-components=1
+
+      - name: Install Python + package
+        working-directory: /tmp/repo
+        run: |
+          set -eu
+          apt-get update -qq
+          apt-get install -y -qq python3 python3-pip python3-venv >/dev/null
+          python3 -m pip install --break-system-packages -e ".[dev]"
+
+      - name: Validate capability registry
+        working-directory: /tmp/repo
+        run: reuse-surface validate --relations --fail-on-warnings
+
+      - name: Compose federated index
+        working-directory: /tmp/repo
+        run: reuse-surface federation compose
+
+      - name: Generate catalog and graph
+        working-directory: /tmp/repo
+        run: |
+          reuse-surface catalog
+          reuse-surface graph --check --fail-on-warnings
+
+      - name: Registry maintain dry-run (informational)
+        working-directory: /tmp/repo
+        run: reuse-surface maintain --all --auto --no-llm || true
+
+      - name: Registry stats (informational)
+        working-directory: /tmp/repo
+        run: reuse-surface stats || true
+
+      - name: Workstation roster federation stats (informational)
+        working-directory: /tmp/repo
+        run: |
+          reuse-surface stats --roster registry/federation/local-repo-roster.yaml \
+            --federation-ready --format json || true
+
+      - name: Planning cohort report (informational)
+        working-directory: /tmp/repo
+        run: reuse-surface report cohorts --planning-min D4 || true
+
+      - name: Registry gap report (informational)
+        working-directory: /tmp/repo
+        run: reuse-surface report gaps || true
+
+      - name: Plan-check smoke test (informational)
+        working-directory: /tmp/repo
+        run: reuse-surface plan-check --intent "smoke test" --format json || true
+
+      - name: Run tests
+        working-directory: /tmp/repo
+        run: pytest -q