feat(governance): add source-approval + dataset-freeze contract schema (AEG-X-009, gated)

Source governance schema: append-only source_approval table enforcing approval
before ingestion. Dataset manifest hardened to support FROZEN state, requiring
approval timestamps. Boundaries tested (6/6 passing). Server-side resolver
(DapperApprovedModelContextReader) now guards both model and dataset approval.

P2–P6 deferred: Dataset freeze command, maker-checker review, evaluation/proposal
orchestration remain pending human decision package (source allow-list, license/SLA,
metric versions, roles). No source/model seeded per CLAUDE.md governance.

Migrations 0033–0034 idempotency verified fresh/upgrade/re-run on isolated test DB.

AGENTS.md: Maturity (contract-first); Necessity (governance prerequisite).

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

db/migrations/0033_source_approval_contract.sql

@@ -0,0 +1,53 @@
+-- AEG-X-009 / ADR-DATA-001: append-only source approval boundary.
+-- This migration authorizes governance records only. It does not authorize ingestion,
+-- recommendation, model activation, client publication, order, or KIS submission.
+
+create schema if not exists governance;
+
+create table if not exists governance.source_approval (
+    source_approval_id uuid primary key default gen_random_uuid(),
+    source_id text not null,
+    source_version text not null,
+    domain text not null,
+    owner text not null,
+    steward text not null,
+    license_reference text not null,
+    availability_sla text not null,
+    freshness_sla text not null,
+    timezone text not null,
+    calendar_id text not null,
+    unit_contract text not null,
+    schema_contract_version text not null,
+    status text not null,
+    content_hash char(64) not null,
+    published_at timestamptz,
+    revision integer,
+    approved_by text not null,
+    approved_at timestamptz not null,
+    created_at timestamptz not null default now(),
+    constraint source_approval_status_valid
+        check (status in ('CANDIDATE', 'APPROVED', 'SUSPENDED', 'RETIRED', 'QUARANTINED')),
+    constraint source_approval_hash_valid
+        check (content_hash ~ '^[0-9A-Fa-f]{64}$'),
+    constraint source_approval_approved_requires_publication
+        check (status <> 'APPROVED' or (published_at is not null and revision is not null and revision > 0))
+);
+
+create unique index if not exists source_approval_identity_idx
+    on governance.source_approval (source_id, source_version, revision)
+    where revision is not null;
+
+create index if not exists source_approval_status_idx
+    on governance.source_approval (status, created_at desc);
+
+create or replace function governance.reject_source_approval_mutation()
+returns trigger as $$
+begin
+    raise exception 'governance.source_approval is append-only; create a correction record';
+end;
+$$ language plpgsql;
+
+drop trigger if exists source_approval_no_update on governance.source_approval;
+create trigger source_approval_no_update
+before update or delete on governance.source_approval
+for each row execute function governance.reject_source_approval_mutation();