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/plan-validator-annotation-fields.test.mjs

@@ -0,0 +1,79 @@
+// tests/validators/plan-validator-annotation-fields.test.mjs
+// Pin forward-compat for v4.2 annotation frontmatter fields on plan.md.
+// Adding revision/source_annotations/annotation_digest/revision_reason must NOT
+// trigger PLAN_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 { validatePlanContent } from '../../lib/validators/plan-validator.mjs';
+
+const STEP_BLOCK = `### Step 1: Do thing
+
+- Files: a.ts
+- Manifest:
+  \`\`\`yaml
+  manifest:
+    expected_paths:
+      - a.ts
+    min_file_count: 1
+    commit_message_pattern: "^feat:"
+    bash_syntax_check: []
+    forbidden_paths: []
+    must_contain: []
+  \`\`\`
+`;
+
+const baseFm = (extra = '') => `---
+plan_version: "1.7"
+profile: balanced${extra}
+---
+
+# Plan
+
+## Implementation Plan
+
+${STEP_BLOCK}
+`;
+
+test('plan-validator forward-compat — baseline (no annotation fields) still valid', () => {
+  const r = validatePlanContent(baseFm(), { strict: true });
+  assert.equal(r.valid, true, JSON.stringify(r.errors));
+});
+
+test('plan-validator forward-compat — accepts revision: 0', () => {
+  const r = validatePlanContent(baseFm('\nrevision: 0'), { strict: true });
+  assert.equal(r.valid, true, JSON.stringify(r.errors));
+});
+
+test('plan-validator forward-compat — accepts revision: 5', () => {
+  const r = validatePlanContent(baseFm('\nrevision: 5'), { strict: true });
+  assert.equal(r.valid, true, JSON.stringify(r.errors));
+});
+
+test('plan-validator forward-compat — accepts source_annotations list-of-dict', () => {
+  const inject = `\nrevision: 1\nsource_annotations:\n  - id: ANN-0001\n    target_artifact: plan.md\n    target_anchor: step-3\n    intent: change\n    comment: "reorder ahead of step 4"\n    timestamp: "2026-05-09T10:00:00Z"`;
+  const r = validatePlanContent(baseFm(inject), { strict: true });
+  assert.equal(r.valid, true, JSON.stringify(r.errors));
+});
+
+test('plan-validator forward-compat — accepts annotation_digest string', () => {
+  const r = validatePlanContent(baseFm('\nrevision: 1\nannotation_digest: 0123456789abcdef'), { strict: true });
+  assert.equal(r.valid, true, JSON.stringify(r.errors));
+});
+
+test('plan-validator forward-compat — accepts revision_reason', () => {
+  const r = validatePlanContent(baseFm('\nrevision: 2\nrevision_reason: "structural step reorder"'), { strict: true });
+  assert.equal(r.valid, true, JSON.stringify(r.errors));
+});
+
+test('plan-validator forward-compat — all 4 fields together with source_findings', () => {
+  const inject = `\nrevision: 3\nrevision_reason: "applied 5 annotations"\nannotation_digest: abc1234567890def\nsource_annotations:\n  - id: ANN-0001\n    target_artifact: plan.md\n    target_anchor: step-3\n    intent: change\nsource_findings:\n  - 0123456789abcdef0123456789abcdef01234567`;
+  const r = validatePlanContent(baseFm(inject), { strict: true });
+  assert.equal(r.valid, true, JSON.stringify(r.errors));
+});
+
+test('plan-validator forward-compat — unrecognized future field tolerated', () => {
+  const r = validatePlanContent(baseFm('\nfuture_v4_3_key: "any"'), { strict: true });
+  assert.equal(r.valid, true, JSON.stringify(r.errors));
+});