[tim-nish]

Summary

Closes #340.

• New tools/tests/test-config-registry: every key in any tool's CONFIG_DEFAULTS, tanuki-config's BUILTIN_DEFAULTS, or a CATALOG entry binding into defaults.* — plus every template key — must have a row in the docs registry table; a missing row fails CI naming the key.
• Registry corrections found by writing the guard:
  • The drive_concurrency row backfilled at triage was wrong — the key reads from the scenarios-file "loop" block only (tools/tanuki-drive:1489-1492), never config.json. Row removed; the preamble now states the loop-block namespace is outside this registry (AC3).
  • contribute_back had no row despite CATALOG binding defaults.contribute_back.{path,schema} — a genuine registry gap; row added (per-target only, both-or-neither, machine-wide copy ignored per contribute_back configuration is global/machine-wide; configuring it for a scratch target mutates shared state #241/F198).
• Template gains driven_env_passthrough: [] and reach_min_turns: 5. Judgment recorded: drive_concurrency deliberately NOT added (not a config.json key).
• Reverse direction (every row needs a built-in default) deliberately not enforced: rows like policy_source legitimately document chain keys with no default (the story question's answer).

Acceptance criteria mapping

• AC1 (code ⊆ registry) → dict literals parsed via ast from all five tools; failure names tool + keys.
• AC2 (template ⊆ registry + catch-up) → template keys asserted; two keys added.
• AC3 (loop-block out of scope, stated) → in the test header comment and the registry preamble.

Review focus

• The registry-domain wording in docs/tanuki-spec.md — it now defines the enforced contract; disagree there, not in the test.
• The contribute_back row's phrasing against spec-den-distill §2.
• Merge-order note: touches docs/tanuki-spec.md (as did Story 5.14: tanuki-spec's paraphrase layer is archived behind pointers #351, merged) — no remaining overlap with open PRs except none known.

Changed areas

tools/tests/test-config-registry (new), docs/tanuki-spec.md, templates/config.example.json.

Test plan

New guard passes; full suite 80/80 locally.

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