docs(master-controls): list all 4 seeded mapping tables + sentinel caveat

The guard probes mc_use_case_mappings as the existence sentinel, but the route
also queries mc_verification, mc_regulations and mc_use_case_sync_state. Document
that they are seeded together and that a half-seeded DB (sentinel present, a
sibling missing) still 500s on the sibling's queries.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

admin-compliance/app/api/sdk/v1/master-controls/route.ts

@@ -15,10 +15,13 @@ const pool = new Pool({ connectionString: dbUrl })
 let metaCache: { at: number; data: unknown } | null = null
 const META_TTL_MS = 120_000
 
-// The use-case mapping tables (mc_use_case_mappings/mc_verification/mc_regulations)
-// are seeded per-environment and may not exist yet on a fresh/unseeded DB. Guard
-// every mapping query so the route degrades to empty filters instead of a 500.
-// Cached with a short TTL so it picks up the tables once that DB gets seeded.
+// The use-case mapping tables (mc_use_case_mappings, mc_verification,
+// mc_regulations, mc_use_case_sync_state) are seeded together per-environment
+// and may not exist yet on a fresh/unseeded DB. We probe mc_use_case_mappings as
+// the existence sentinel and guard every mapping query so the route degrades to
+// empty filters instead of a 500. Short TTL so it picks up the tables once seeded.
+// NB: the sentinel assumes the siblings are seeded together — a half-seeded DB
+// (mappings present but e.g. mc_regulations missing) would still 500 on those.
 let mappingTablesCache: { at: number; present: boolean } | null = null
 async function hasMappingTables(): Promise<boolean> {
   if (mappingTablesCache && Date.now() - mappingTablesCache.at < 300_000) {