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/etude-lexical-markdown-editorconfig-db4f54/fixed.ts

@@ -0,0 +1,30 @@
+// Provenance: dayflower/etude-lexical-markdown  (fixed).
+// repo: dayflower/etude-lexical-markdown
+// commit: db4f54b1ab80ad596de6425e84f90aa781c49999
+// parent: 1c865815d05b072f4973388c3ac66b6696d9efde
+// commit_url: https://github.com/dayflower/etude-lexical-markdown/commit/db4f54b1ab80ad596de6425e84f90aa781c49999
+// cve: 
+// license: MIT
+// function: deepMergeInto
+// relpath: src/config/editorConfig.ts
+// provenance: agent
+// mechanism: prototype_pollution
+
+function deepMergeInto(
+  target: Record<string, unknown>,
+  source: Record<string, unknown>,
+): Record<string, unknown> {
+  for (const key of Object.keys(source)) {
+    if (isForbiddenKey(key)) continue;
+    const sourceValue = source[key];
+    if (sourceValue === undefined) continue;
+    if (isPlainObject(sourceValue)) {
+      const targetValue = target[key];
+      const nested = isPlainObject(targetValue) ? targetValue : {};
+      target[key] = deepMergeInto(nested, sourceValue);
+    } else {
+      target[key] = sourceValue;
+    }
+  }
+  return target;
+}