test(voyage): pin forward-compat for revision/source_annotations/annotation_digest/revision_reason — v4.2 Step 2

3 new test files, 24 cases (8 per validator):
- baseline (no annotation fields) still valid
- revision: 0 / revision: 5 accepted
- source_annotations list-of-dict accepted
- annotation_digest string accepted
- revision_reason accepted
- all 4 fields together accepted
- unrecognized future field tolerated (forward-compat policy)

Pin against future strict-key refactors. No production code change — pure regression pin.

plugins/voyage/tests/validators/brief-validator-annotation-fields.test.mjs

@@ -0,0 +1,87 @@
+// tests/validators/brief-validator-annotation-fields.test.mjs
+// Pin forward-compat for v4.2 annotation frontmatter fields on brief.md.
+// Adding revision/source_annotations/annotation_digest/revision_reason must NOT
+// trigger BRIEF_UNKNOWN_FIELD or similar — validator is purely additive-tolerant
+// per source_findings precedent. No code change required; this test pins the policy.
+
+import { test } from 'node:test';
+import { strict as assert } from 'node:assert';
+import { validateBriefContent } from '../../lib/validators/brief-validator.mjs';
+
+const BASE_BRIEF = `---
+type: trekbrief
+brief_version: "2.0"
+created: 2026-05-09
+task: "Annotated revision for testing forward-compat"
+slug: ann-fwd-compat
+project_dir: .claude/projects/2026-05-09-ann-fwd-compat/
+research_topics: 0
+research_status: skipped
+auto_research: false
+interview_turns: 1
+source: interview
+---
+
+# Task: Annotated revision
+
+## Intent
+
+Why.
+
+## Goal
+
+What.
+
+## Success Criteria
+
+- Done.
+`;
+
+test('brief-validator forward-compat — baseline (no annotation fields) still valid', () => {
+  const r = validateBriefContent(BASE_BRIEF, { strict: true });
+  assert.equal(r.valid, true, JSON.stringify(r.errors));
+});
+
+test('brief-validator forward-compat — accepts revision: 0', () => {
+  const t = BASE_BRIEF.replace('---\ninterview_turns: 1', '---\ninterview_turns: 1\nrevision: 0');
+  const r = validateBriefContent(t, { strict: true });
+  assert.equal(r.valid, true, JSON.stringify(r.errors));
+});
+
+test('brief-validator forward-compat — accepts revision: 5', () => {
+  const t = BASE_BRIEF.replace('source: interview', 'source: interview\nrevision: 5');
+  const r = validateBriefContent(t, { strict: true });
+  assert.equal(r.valid, true, JSON.stringify(r.errors));
+});
+
+test('brief-validator forward-compat — accepts source_annotations list-of-dict', () => {
+  const inject = `\nrevision: 1\nsource_annotations:\n  - id: ANN-0001\n    target_artifact: brief.md\n    target_anchor: intent\n    intent: change\n    comment: "tighten the intent paragraph"\n    timestamp: "2026-05-09T10:00:00Z"`;
+  const t = BASE_BRIEF.replace('source: interview', 'source: interview' + inject);
+  const r = validateBriefContent(t, { strict: true });
+  assert.equal(r.valid, true, JSON.stringify(r.errors));
+});
+
+test('brief-validator forward-compat — accepts annotation_digest string', () => {
+  const t = BASE_BRIEF.replace('source: interview', 'source: interview\nrevision: 1\nannotation_digest: abc123def4567890');
+  const r = validateBriefContent(t, { strict: true });
+  assert.equal(r.valid, true, JSON.stringify(r.errors));
+});
+
+test('brief-validator forward-compat — accepts revision_reason for non-additive revision', () => {
+  const t = BASE_BRIEF.replace('source: interview', 'source: interview\nrevision: 2\nrevision_reason: "restructured Goals section"');
+  const r = validateBriefContent(t, { strict: true });
+  assert.equal(r.valid, true, JSON.stringify(r.errors));
+});
+
+test('brief-validator forward-compat — all 4 fields together still valid', () => {
+  const inject = `\nrevision: 3\nrevision_reason: "applied 5 annotations"\nannotation_digest: 0123456789abcdef\nsource_annotations:\n  - id: ANN-0001\n    target_artifact: brief.md\n    target_anchor: goal\n    intent: change`;
+  const t = BASE_BRIEF.replace('source: interview', 'source: interview' + inject);
+  const r = validateBriefContent(t, { strict: true });
+  assert.equal(r.valid, true, JSON.stringify(r.errors));
+});
+
+test('brief-validator forward-compat — unrecognized future field still tolerated (forward-compat policy)', () => {
+  const t = BASE_BRIEF.replace('source: interview', 'source: interview\nfuture_v4_3_field: "anything"');
+  const r = validateBriefContent(t, { strict: true });
+  assert.equal(r.valid, true, JSON.stringify(r.errors));
+});