Complete REUSE-WP-0004: CI, overlap detection, and catalog generation

Add Gitea CI workflow for registry validation, reuse-surface overlaps and
catalog commands, generated catalog artifacts, and documentation updates
closing gap analysis priorities 9-11.

.gitea/workflows/ci.yml

@@ -0,0 +1,25 @@
+name: ci
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  validate-registry:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out source
+        uses: actions/checkout@v4
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.12"
+
+      - name: Install package
+        run: python -m pip install -e .
+
+      - name: Validate capability registry
+        run: reuse-surface validate