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/djangoat-views-user-view/fixed.py

@@ -0,0 +1,18 @@
+# Provenance: Contrast-Security-OSS/DjanGoat user_view (fixed).
+# repo: Contrast-Security-OSS/DjanGoat
+# commit: 082c88bfefced508ae083b92b459c808f95e905e
+# parent: 082c88bfefced508ae083b92b459c808f95e905e
+# commit_url: https://github.com/Contrast-Security-OSS/DjanGoat/blob/082c88bfefced508ae083b92b459c808f95e905e/app/views/users/views.py#L74
+# cve: 
+# license: MIT
+# function: user_view
+# relpath: app/views/users/views.py
+# provenance: human
+# mechanism: source_reaches_sink
+
+    def parse_field(field):
+        valid_fields = ["ip_address", "referrer", "user_agent"]
+        if field in valid_fields:
+            return field
+        else:
+            return '1'