review: spec-first fanout and ratchet move to toolchain #7584

Parent

Refs #7555. Source: PLAN Phase 16, topic poteto-review. Thread: review.

Depends on

• config-cascade: settings resolution and convention home #7571 Settings resolution and convention home
• standards: per-concern standards layout #7583 Standards layout (per-concern files feed fanout criteria slices)

Outcome

/review:fanout reports spec findings first under their own heading, then standards, with an act-on
cap set from an eval; /review:ratchet becomes /toolchain:ratchet with a per-file baseline mode.

Decisions

• /review:fanout gains Lauren's interrogate lead judgment: spec findings first under their own
  heading, then standards; act-on cap per heading (setting from the Q160 eval); agreement map covers
  both; stays a code review (D101, Q159). Origin: combined (Lauren's interrogate; Matt keeps the
  two axes separate).
• Criteria from per-concern standards files loaded as criteria slices; a code-quality lens slice with
  a configurable file-size threshold that only flags long files on targeted work (D101, Q135).
• Fanout documented for design stub scaffolds (Q169). Review criteria stay with the reviewer;
  implementation loads only paved-path entries for the paths it touches (D98, Q153).
• Standards discovery names a root CODING_STANDARDS.md and CONTRIBUTING.md as rung-4 sources
  (Q523).
• /review:ratchet moves to /toolchain:ratchet; name stays; the limit is "the ceiling"; per-file
  baseline mode using each linter's native baseline (D36, D63, D81, Q513; Lauren's "fail only
  when a change adds more"). The zero-entry baseline rule (Q181) lives in the /toolchain:ratchet
  reference (B8).
• Lint rollout: codemod then error when mechanical, else per-file baseline at error severity; break
  glass is an inline exception with reason, expiry and a human's approval, as a team setting (D64,
  Q23).
• Research tag: fanout reviewer-diversity eval (12 diffs, 4 arms, 3 runs) settles the lens default,
  panel placement and the act-on cap (Q134, Q160, D101).

Key interfaces

From the design's module layout: "review: /review:fanout gains spec-first judgment and a
code-quality lens slice; /review:audit-enforceability moves to corrections; /review:ratchet
moves to /toolchain:ratchet." "toolchain: gains /toolchain:ratchet (per-file baseline mode)."
Settings: "fanout act-on cap from the Q160 eval."

Slices, filed when this phase starts: fanout-spec-first, fanout-eval-and-cap, ratchet-move.

Done when

• The ratchet skill lives under toolchain, not review, and
  rg -n 'review:ratchet' plugins docs --glob '!**/CHANGELOG.md' --glob '!.changes/**' prints
  nothing.
• The five zero-entry baseline files that exist on main are deleted with their reading code.
• The fanout eval slice carries a Probe result: comment before the act-on cap merges.

Out of scope

• /review:audit-enforceability (moves with the corrections thread).