WP-0016 finished: interactive registry maintain with llm-connect automation

Closes the registry maintenance loop from inside each domain repo:
interactive prompting for judgment calls, full automation for safe and
high-confidence changes, both backed by the llm-connect HTTP bridge.

- New modules: maintain.py, maintain_llm.py, patches.py, interactive.py
- Schema: schemas/registry-patch.schema.json
- CLI: reuse-surface maintain; establish --scaffold --hook
- Sibling templates: Makefile fragment, pre-commit hook
- Deterministic signal collectors extended; validate cwd auto-detect
- Docs, gap priority 28, SCOPE update
- Tests: test_maintain.py, test_interactive.py (59 pytest total)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

templates/git-hook.pre-commit.registry

@@ -0,0 +1,6 @@
+#!/bin/sh
+# Optional pre-commit hook: deterministic registry sync when registry/ changes.
+if git diff --cached --name-only | grep -q '^registry/'; then
+  reuse-surface maintain --all --auto --no-llm || exit 1
+  git add registry/
+fi