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.

AGENTS.md

@@ -124,6 +124,10 @@ artifacts.
 # Registry validation (schema + index drift)
 .venv/bin/reuse-surface validate
 
+# Overlap and catalog generation
+.venv/bin/reuse-surface overlaps
+.venv/bin/reuse-surface catalog
+
 # Repository hygiene
 rg --files
 git diff --check
@@ -149,6 +153,9 @@ The generated instruction in older workplans says `make fix-consistency
 REPO=reuse-surface`; that is still valid when `uv` is installed and on PATH.
 On this workstation, the `.venv/bin/python` fallback has been verified.
 
+CI runs `reuse-surface validate` on push and pull requests via
+`.gitea/workflows/ci.yml`.
+
 ### Run
 
 There is no local service to run from this repository.