feat(pair-corpus-honesty): add vibe-py, vfc-js and agent-vfc slices with mechanism vocabulary

Tasks 1.1, 5.1, 5.2, 5.4 and the data half of 5.3.

- mechanisms.toml: closed vocabulary v1 (20 ids) every expected row cites.
- vibe-py: 35 Real-Vuln-Benchmark pairs (Apache-2.0), human provenance only
  because the LLM-generated repositories carry no license (escalated).
- vfc-js: 17 Node fix-commit pairs harvested upstream (MIT/Apache-2.0),
  SecBench.js itself is not vendored (no license); sinks derived on 13/17.
- agent-vfc: 29 agent-trailer fixes as catalog-candidates.toml plus
  REVIEW.md; the loaded catalog stays empty until a human reviews them.
- datasets.toml and README document every slice and its review status.

Co-Authored-By: Claude Fable 5.1 <[email protected]>
Claude-Session: https://claude.ai/code/session_01T7XD7x5KonMdmGRkp63EQG

benchmarks/pairs/agent-vfc/anastasios-pw-session-14ec1a/fixed.ts

@@ -0,0 +1,38 @@
+// Provenance: Anas329796/Anastasios  (fixed).
+// repo: Anas329796/Anastasios
+// commit: 14ec1ac50f9e4e255d875236d30129c6207401d4
+// parent: adb7b0d5d6b81c46d56451c709e7eac9d0dc93fb
+// commit_url: https://github.com/Anas329796/Anastasios/commit/14ec1ac50f9e4e255d875236d30129c6207401d4
+// cve: 
+// license: MIT
+// function: isTopLevelNavigationRequest
+// relpath: extensions/browser/src/browser/pw-session.ts
+// provenance: agent
+// mechanism: source_reaches_sink
+
+function isTopLevelNavigationRequest(page: Page, request: Request): boolean {
+  let sameMainFrame = false;
+  try {
+    sameMainFrame = request.frame() === page.mainFrame();
+  } catch {
+    // Frame resolution can fail during redirect/renderer churn; fail closed.
+    sameMainFrame = true;
+  }
+  if (!sameMainFrame) {
+    return false;
+  }
+
+  try {
+    if (request.isNavigationRequest()) {
+      return true;
+    }
+  } catch {
+    // Ignore and fall back to resource-type check below.
+  }
+
+  try {
+    return request.resourceType() === "document";
+  } catch {
+    return false;
+  }
+}