test: add triage resolver unit tests, plan-eng coverage audit E2E, and triage E2E

- TEST_FAILURE_TRIAGE resolver: 6 unit tests verifying all triage steps (T1-T4),
  REPO_MODE branching, and safety default for ambiguous failures
- plan-eng-coverage-audit E2E: tests /plan-eng-review coverage audit codepath
  (gap identified during eng review — existed on neither branch)
- ship-triage E2E: planted-bug fixture with in-branch (truncate null) and
  pre-existing (divide-by-zero) failures; verifies correct classification
- Touchfile entries for diff-based test selection

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

test/gen-skill-docs.test.ts

@@ -520,6 +520,46 @@ describe('TEST_COVERAGE_AUDIT placeholders', () => {
   });
 });
 
+// --- {{TEST_FAILURE_TRIAGE}} resolver tests ---
+
+describe('TEST_FAILURE_TRIAGE resolver', () => {
+  const shipSkill = fs.readFileSync(path.join(ROOT, 'ship', 'SKILL.md'), 'utf-8');
+
+  test('contains all 4 triage steps', () => {
+    expect(shipSkill).toContain('Step T1: Classify each failure');
+    expect(shipSkill).toContain('Step T2: Handle in-branch failures');
+    expect(shipSkill).toContain('Step T3: Handle pre-existing failures');
+    expect(shipSkill).toContain('Step T4: Execute the chosen action');
+  });
+
+  test('T1 includes classification criteria (in-branch vs pre-existing)', () => {
+    expect(shipSkill).toContain('In-branch');
+    expect(shipSkill).toContain('Likely pre-existing');
+    expect(shipSkill).toContain('git diff origin/');
+  });
+
+  test('T3 branches on REPO_MODE (solo vs collaborative)', () => {
+    expect(shipSkill).toContain('REPO_MODE');
+    expect(shipSkill).toContain('solo');
+    expect(shipSkill).toContain('collaborative');
+  });
+
+  test('solo mode offers fix-now, TODO, and skip options', () => {
+    expect(shipSkill).toContain('Investigate and fix now');
+    expect(shipSkill).toContain('Add as P0 TODO');
+    expect(shipSkill).toContain('Skip');
+  });
+
+  test('collaborative mode offers blame + assign option', () => {
+    expect(shipSkill).toContain('Blame + assign GitHub issue');
+    expect(shipSkill).toContain('gh issue create');
+  });
+
+  test('defaults ambiguous failures to in-branch (safety)', () => {
+    expect(shipSkill).toContain('When ambiguous, default to in-branch');
+  });
+});
+
 // --- {{SPEC_REVIEW_LOOP}} resolver tests ---
 
 describe('SPEC_REVIEW_LOOP resolver', () => {