docs(corpus-seeded-mechanisms): close the spec after six review rounds

- tasks.md: all tasks checked; rounds 1-6 recorded with RED evidence,
  measured leave-one-out and admission numbers, and the recorded design
  deviations.
- spec.json: completed 2026-09-05.
- roadmap: corpus-seeded-mechanisms marked completed; the loop is closed
  end to end (export -> improve admits under the holdout clause -> scan
  searches -> reports name the mechanism).

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

.kiro/steering/roadmap.md

@@ -51,6 +51,8 @@ Leave-one-out (corpus-seeded-mechanisms, 2026-09-05; the corpus as a teacher, ne
 | github | 6 | 0 | 6 | 0.000 | 0 | advisory tier |
 | vfc-js | 17 | 0 | 17 | 0.000 | 0 | advisory tier |
 
+The loop is closed: `ousast mechanisms export` writes candidates, `ousast improve --pair-catalog` admits the ones that recover a holdout pair without leaking (per-profile clause over variant search; `mechanism_leak`/`mechanism_no_gain` revert byte for byte), the scan searches the admitted store and reports name the mechanism and its known fix. Measured 2026-09-05 on the `python-vulnerable` benchmark target with the vibe-py candidates: 4 records admitted in round 1 (`execute/1 parameter` taught by 7 pairs among them), human holdout profile pair_correct 0 -> 6 of 17, Youden 0 -> +0.353, round 2 `no_proposals`.
+
 Measured 2026-09-05 after review tiers (Req 9) and pointer slices (Req 10): vibe-py 115 = 35 vendored human (13/35, Youden +37.1%) + 80 `agent` pointer pairs over the 40 LLM-generated Real-Vuln repositories (0/80, Youden 0.0; the LLM-repo baseline, scored by the nightly `pairs --slice vibe-py --pointers` only, never in tests or gates); agent-vfc 59 = 29 vendored + 30 pointer, tier `title`, 1/59, Youden 0.0, 2 unresolved labels; sast, vfc-js, vfc unchanged; detection/map/local-pair gate outputs byte-identical to the pre-spec commit. Only `seeded`/`reviewed` pairs gate the improve loop. Carry-forwards: `language_unsupported` loss counter and multi-line C/C++ declarator rescue (overlay-ir-completeness), `profiles_ungated` reporting and an offline test for the agent-vfc pointer builder (corpus-seeded-mechanisms).
 
 sast: java-sqli moved MISS→LEAK (coverage counted on both sides; the fixed twin leaks via parameter-as-source). vfc: recall fell to zero because every label now names a function and no C detection lands inside it; that is the honest baseline the engine specs measure against.
@@ -82,7 +84,7 @@ sast: java-sqli moved MISS→LEAK (coverage counted on both sides; the fixed twi
 - [x] tree-sitter-overlay-extra -- Optional extra: tree-sitter + grammars, one CST walker, `quick` stays zero-dep. Dependencies: none
 - [x] real-world-vfc-slice -- Harvest reviewed function-level vuln/fix pairs from large projects (Firefox/gecko-dev, Chromium, OpenSSL, …) as an honesty slice. Seed is testable (`ousast pairs --slice vfc`). Dependencies: none. **Closed 2026-09-04, superseded by pair-corpus-honesty on the corpus/scorer plane.**
 - [x] pair-corpus-honesty -- Scorer counts coverage and matches by function; labels carry mechanism/provenance/split/known_limit; harvest anchors at the declarator with line-range and hunk modes; sast hygiene; new slices `vibe-py` (Real-Vuln-Benchmark), `vfc-js` (SecBench.js fix commits), `agent-vfc` (agent-trailer fixes); deterministic provenance fingerprint; per-profile improve acceptance; review tiers and pointer slices (amendment). Dependencies: none (supersedes real-world-vfc-slice). **Completed 2026-09-05 (11 review rounds).**
-- [ ] corpus-seeded-mechanisms -- Every seeded or reviewed pair becomes a mechanism record (source shape, sink shape, guard the fix added); structural variant search over the scanned tree proposes matches as `variant` findings that the overlay and sandbox verify; leave-one-out recall on the pair corpus is the corpus's own detection rate; the improve loop gains a recall-raising `mechanisms` lever under the per-profile holdout gate. Principle: recall first under a false-positive ceiling, per profile. Dependencies: pair-corpus-honesty (tiers, pointer slices)
+- [x] corpus-seeded-mechanisms -- Every seeded or reviewed pair becomes a mechanism record (source shape, sink shape, guard the fix added); structural variant search over the scanned tree proposes matches as `variant` findings that the overlay and sandbox verify; leave-one-out recall on the pair corpus is the corpus's own detection rate; the improve loop gains a recall-raising `mechanisms` lever under the per-profile holdout gate. Principle: recall first under a false-positive ceiling, per profile. Dependencies: pair-corpus-honesty (tiers, pointer slices). **Completed 2026-09-05 (6 review rounds).**
 - [ ] reachability-flow-model -- Name-resolved call graph over `FunctionIR`; per-function taint summaries composed along the graph into path records; graph reachability drives rank, map, worth-fixing; hunter gets `path_context` and hunter findings with a locatable sink become sandbox candidates; closed-kind fact oracle with candidate cache; `facts` improve lever under the per-profile gate; fix points ranked by reachable risk removed. Dependencies: pair-corpus-honesty
 - [ ] overlay-ir-completeness -- Shared CST walker completeness (C `init_declarator`, lvalue paths for field stores, per-grammar literal kinds, local ERROR-node tolerance, multi-line C/C++ declarators the walker names `<anon>` and `functions.py`'s one-line rescue cannot name: `chromium-cve-2022-2162`, `openssl-cve-2025-69421`; a Scorer-side multi-line-aware rescue is the cheaper alternative) plus Python parity with stdlib ast (f-string constness, augmented assignment, kwargs); injection-regime facts: container/transformer taint, `weak_literals` consulted, parameter sources off for injection. Measured on sast and vibe-py. Dependencies: pair-corpus-honesty
 - [ ] guard-dominance-regime -- Guard and Use IR records; guard dominance by nesting or early exit; memory sinks (memcpy/malloc/deref) with operand roles, nullable callees, out-param transformers, fixed-array capacity; same regime applied to web absence bugs (route auth guard, identity from auth context). Consumes path records. Measured on vfc, vfc-js, agent-vfc. Dependencies: reachability-flow-model, overlay-ir-completeness