feat(#1726): G1-G6 portability AST rules; fix all offenders; delete the ratchet (Phase 4) (#1731)

Phase 4 of epic #1702. Closes #1726.

tests/bug-1967-cache-invalidation.test.cjs

@@ -81,7 +81,7 @@ describe('buildStateFrontmatter cache invalidation (#1967)', () => {
 
     // Read back and parse frontmatter to verify it reflects 2 phases, not 1
     const result = fs.readFileSync(statePath, 'utf-8');
-    const fmMatch = result.match(/^---\n([\s\S]*?)\n---/);
+    const fmMatch = result.match(/^---\r?\n([\s\S]*?)\r?\n---/);
     assert.ok(fmMatch, 'STATE.md should have frontmatter after writeStateMd');
 
     const fm = fmMatch[1];