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/vibe-py/extremely-vulnerable-flask-app-account-search/vuln.py

@@ -0,0 +1,25 @@
+# Provenance: manuelz120/extremely-vulnerable-flask-app search (vuln).
+# repo: manuelz120/extremely-vulnerable-flask-app
+# commit: d5d8875559e21222bbbaadb7b9f0af592c6eb7fa
+# parent: d5d8875559e21222bbbaadb7b9f0af592c6eb7fa
+# commit_url: https://github.com/manuelz120/extremely-vulnerable-flask-app/blob/d5d8875559e21222bbbaadb7b9f0af592c6eb7fa/routes/account.py#L33
+# cve: 
+# license: GPL-3.0
+# function: search
+# relpath: routes/account.py
+# provenance: human
+# mechanism: source_reaches_sink
+
+def search():
+    search_param = request.args.get('search', '')
+    with Session() as session:
+        session.query(Note)
+
+        personal_notes = session.query(Note).filter(
+            Note.user_id == current_user.id,
+            text(f"text like '%{search_param}%'")).all()
+        return render_template(
+            'search.html',
+            search=search_param,
+            personal_notes=personal_notes,
+        )