feat(sdk): strip frontmatter region before UAT item scan (#3184)

Cycle 5 of ~15: introduces stripMarkdownInjection helper.
First pass strips the YAML frontmatter region so injected
'### N. item' patterns inside frontmatter literal blocks
cannot be mistaken for real UAT items.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

sdk/src/query/phase-uat-passed.test.ts

@@ -109,4 +109,36 @@ result: issue
       await rm(localTmp, { recursive: true, force: true });
     }
   });
+
+  it('ignores ### item content inside YAML frontmatter region', async () => {
+    const localTmp = await mkdtemp(join(tmpdir(), 'gsd-uat-c5-'));
+    try {
+      const phaseDir = join(localTmp, '.planning', 'phases', '05-frontmatter-injection');
+      await mkdir(phaseDir, { recursive: true });
+      const content = `---
+status: complete
+phase: 5
+source: roadmap
+started: 2026-05-18T00:00:00Z
+updated: 2026-05-18T00:00:00Z
+malicious_demo: |
+### 1. Frontmatter-injected item
+expected: nothing
+result: pass
+---
+
+### 1. Real item
+expected: real thing
+result: pass
+`;
+      await writeFile(join(phaseDir, '05-HUMAN-UAT.md'), content);
+
+      const result = await isPhaseUatPassed(localTmp, '5');
+      expect(result.passed).toBe(true);
+      expect(result.items.length).toBe(1);
+      expect(result.items[0].name).toBe('Real item');
+    } finally {
+      await rm(localTmp, { recursive: true, force: true });
+    }
+  });
 });

sdk/src/query/phase-uat-passed.ts

@@ -35,11 +35,23 @@ interface UatItem {
   result: string;
 }
 
+/**
+ * Strip regions from file content that could contain markdown-shaped text
+ * but should not be treated as UAT items (frontmatter, code fences, etc.).
+ * Passes are applied in order; each returns a sanitised string.
+ */
+function stripMarkdownInjection(content: string): string {
+  // Pass 1: strip YAML frontmatter region (---\n...\n---)
+  let s = content.replace(/^---\r?\n[\s\S]*?\r?\n---/m, '');
+  return s;
+}
+
 function parseAllUatItems(content: string): UatItem[] {
+  const sanitised = stripMarkdownInjection(content);
   const items: UatItem[] = [];
   UAT_ITEM_PATTERN.lastIndex = 0;
   let m: RegExpMatchArray | null;
-  while ((m = UAT_ITEM_PATTERN.exec(content)) !== null) {
+  while ((m = UAT_ITEM_PATTERN.exec(sanitised)) !== null) {
     const [, num, name, expected, result] = m;
     items.push({
       test: parseInt(num, 10),