phase0: add architecture guardrails, CI gates, per-language AGENTS.md

Non-negotiable structural rules that apply to every Claude Code session in
this repo and to every commit, enforced via three defense-in-depth layers:

  1. PreToolUse hook in .claude/settings.json blocks any Write/Edit that
     would push a file past the 500-line hard cap. Auto-loads for any
     Claude session in this repo regardless of who launched it.
  2. scripts/githooks/pre-commit (installed via scripts/install-hooks.sh)
     enforces the LOC cap, freezes migrations/ unless [migration-approved],
     and protects guardrail files unless [guardrail-change] is present.
  3. .gitea/workflows/ci.yaml gets loc-budget + guardrail-integrity jobs,
     plus mypy --strict on new Python packages, tsc --noEmit on Node
     services, and a syft+grype SBOM scan.

Per-language conventions are documented in AGENTS.python.md / AGENTS.go.md /
AGENTS.typescript.md at the repo root — layering (router->service->repo for
Python, hexagonal for Go, colocation for Next.js), tooling baseline, and
explicit "what you may NOT do" lists.

Adds scripts/check-loc.sh (soft 300 / hard 500, reports 205 hard and 161
soft violations in the current codebase) plus .claude/rules/loc-exceptions.txt
(initially empty — the list is designed to shrink over time).

Per-service READMEs for all 10 services + PHASE1_RUNBOOK.md for the
backend-compliance refactor. Skeleton packages (compliance/{domain,
repositories,schemas}) are the landing zone for the clean-arch rewrite that
begins in Phase 1.

CLAUDE.md is prepended with the six non-negotiable rules.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.claude/rules/loc-exceptions.txt

@@ -0,0 +1,8 @@
+# loc-exceptions.txt — files allowed to exceed the 500-line hard cap.
+#
+# Format: one repo-relative path per line. Comments start with '#' and are ignored.
+# Each exception MUST be preceded by a comment explaining why splitting is not viable.
+#
+# Phase 0 baseline: this list is initially empty. Phases 1-4 will add grandfathered
+# entries as we encounter legitimate exceptions (e.g. large generated data tables).
+# The goal is for this list to SHRINK over time, never grow.