feat(pair-corpus-honesty): review tiers on every pair, agent-vfc loads at tier title

Tasks 8.1, 7.1 (tests) and the re-scoped 5.3.

- pairs.py: review_tier in {seeded, advisory, title, reviewed} with
  per-slice defaults (local reviewed, vibe-py seeded, sast/vfc/vfc-js/
  github advisory, agent-vfc title); reviewer = "pending" means title, a
  named reviewer means reviewed, reviewed without a reviewer is rejected;
  per_tier metrics in the payload; select_tier and GATING_TIERS for the
  improve loop.
- catalog_gen.py: stamps review_tier (and reviewer) on every generated
  row and training manifest row; title rows enter catalog.toml; the
  catalog-candidates.toml queue is retired; precedence matches the loader.
- agent-vfc: 29 title-tier rows load and score (0/29, Youden 0.0, the
  honest unreviewed baseline); local rows name their reviewer.
- Tests: tier defaults, loader rejections, per_tier payload, the Req 8.1
  catalog-on-disk / stage-1 exclusion proof and per-slice CLI checks.

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

benchmarks/pairs/catalog.toml

@@ -8,6 +8,8 @@ slice = "local"
 language = "python"
 origin = "in-tree-fixture"
 license = "in-tree"
+review_tier = "reviewed"
+reviewer = "Marius Ciepluch"
 vuln = "../fixtures/python-vulnerable/app.py"
 fixed = "../fixtures/python-vulnerable/safe.py"
 relpath = "app.py"
@@ -21,6 +23,8 @@ slice = "local"
 language = "javascript"
 origin = "in-tree-fixture"
 license = "in-tree"
+review_tier = "reviewed"
+reviewer = "Marius Ciepluch"
 vuln = "../fixtures/javascript-vulnerable/src/app.js"
 fixed = "../fixtures/javascript-vulnerable/src/safe.js"
 relpath = "src/app.js"
@@ -34,6 +38,8 @@ slice = "local"
 language = "c_cpp"
 origin = "in-tree-fixture"
 license = "in-tree"
+review_tier = "reviewed"
+reviewer = "Marius Ciepluch"
 vuln = "../fixtures/cpp-damn-vulnerable/src/buffer.cpp"
 fixed = "../fixtures/cpp-damn-vulnerable/src/safe.cpp"
 relpath = "src/buffer.cpp"