feat(real-world-vfc-slice): add labeled OpenSSL/Firefox/Chromium/curl pair corpus

Harvest 176 isolated vuln-vs-fix functions (109 CVEs, 352 training rows)
into benchmarks/pairs/vfc with provenance and a JSONL training manifest.
Score the slice as an honesty dashboard (ousast pairs --slice vfc);
keep the pair gate on the local fixtures only.

.kiro/specs/real-world-vfc-slice/brief.md

@@ -0,0 +1,54 @@
+# Brief: real-world-vfc-slice
+
+## Problem
+
+Operators care whether the harness fires on a real buggy snapshot and stays quiet after the patch — Firefox, Chromium, OpenSSL — not whether OWASP BenchmarkTest00074 is a TP. The labeled SAST slice is 11 textbook files. Overlay Youden there is **worse** than inventory (+9.09% → 0%). We cannot tell if the tool got better on messy product code.
+
+## Current State
+
+Slices today: `local` (CI 100%), `github` (6 vendored functions: SVEN, hutool, node-serialize), `sast` (OWASP/Juliet). `datasets.toml` already points at CVEfixes, MoreFixes, CWE-Bench-Java, Vul4J. Nothing is harvested from gecko-dev / Firefox. Whole mozilla-central is not in-tree (and should not be). FixFox (Zenodo) is embargoed until 2030. Firefox security commit messages are often scrubbed of “security” words, so grep-the-log is a bad miner.
+
+Measured on the current 11-pair **sast** slice (2026-09-04):
+
+| Scorer | pair_correct | vuln recall | silent-on-fix | Youden |
+|--------|--------------|-------------|---------------|--------|
+| Inventory (regex) | 2/11 (18%) | 54.5% | 54.5% | **+9.09%** |
+| Overlay (current) | 2/11 (18%) | 45.5% | 54.5% | **0%** |
+
+The only overlay change vs inventory on that slice: `owasp-python-codeinj` went from LEAK (regex hit both sides) to MISS (ConfigParser heap → `flow_incomplete`, no promote). C/Java Juliet goodG2B still leak because those languages are unadjudicated and scoring falls back to inventory.
+
+## Desired Outcome
+
+A new pair slice (e.g. `vfc`) of **reviewed, isolated function pairs** from large projects, including Firefox/gecko-dev when a public fix commit exists in CVEfixes/MoreFixes. Offline CI. Honesty dashboard like `github`, not a 90% smoke gate. Overlay scoring once tree-sitter can parse C/JS/Java; inventory scoring until then. Provenance on every file (repo, commit, CVE, license).
+
+## Approach
+
+Do not clone Firefox. Filter public VFC databases for `gecko-dev` / `mozilla-firefox/firefox`, `chromium`, `openssl`, `curl`, plus existing CWE-Bench-Java. Extract the changed function before/after. Human-review labels (DiverseVul ~60% is not ground truth). Cap the runnable catalog (tens of pairs, not thousands). Prefer injection/XSS/path CWEs the overlay can talk about; keep UAF/buffer overflows as known inventory-only leaks until a later memory-safety spec.
+
+## Scope
+
+- **In**: harvest script or documented procedure; catalog slice; provenance headers; overlay-vs-inventory scoreboard on that slice; dataset.toml pointers for Firefox/Chromium.
+- **Out**: Vendoring mozilla-central; live Bugzilla scraping; making Youden a merge gate; buffer-size semantics; tree-sitter packaging (owned by `tree-sitter-overlay-extra`).
+
+## Boundary Candidates
+
+- Catalog schema / slice name vs pair eval scoring
+- Harvest tooling vs vendored excerpts
+
+## Out of Boundary
+
+- Parser extra, Joern, improve-loop auto-facts, `LANGUAGE_MANIFESTS`
+
+## Upstream / Downstream
+
+- **Upstream**: `pairs.py` catalog format; `propose-adjudicate-prove` overlay scoring
+- **Downstream**: improve-loop signals from real misses; later memory-safety spec can reuse the same slice
+
+## Existing Spec Touchpoints
+
+- **Extends**: pair catalog only (new slice). Does not change smoke gate.
+- **Adjacent**: `tree-sitter-overlay-extra` (C/Java overlay on this slice once the extra exists)
+
+## Constraints
+
+Isolated functions, same `relpath` vuln/fixed. License in the header. No 16 GB dumps in git. Firefox pairs only when a public git commit pair exists — MFSA text without a commit is not a pair.