docs(skill): treat shallow/file_split as advisory and add stop rule

[kevmoo]

The dart-cognitive-complexity skill pushes agents to clear every shallow and file_split finding, which caused over-refactoring and regressions in dogfood runs.

Changes

• Stop rule: only declarations above the threshold are work items. When max CC <= threshold, report done and stop; anything further needs a user ask.
• Advisory, not gates: shallow and file_split are documented as optional review aids. Removed the "batch re-inline SAFE_INLINE" triage option and every --fail-on-safe-inline gate recommendation. The findings-table action now reads "Review: consider re-inlining if ...".
• Keep/revert heuristics (new §5.3): keep de-duplication, guard clauses, and named step helpers. Don't inline helpers with same-shape siblings or meaningful names/docs, don't make style-only edits, and don't split files without a cohesive name (no barrels or cycles).
• Hot-loop rule (new §5.4): benchmark before splitting per-element kernels. Prefer an inline kernel with // cognitive_complexity:ignore on the line before the declaration, plus a reason comment.
• Blind self-review: for diffs over ~300 lines, a fresh agent or human reviewer given only the before/after trees and diff judges each change.
• refactoring_recipes.md: Pattern G no longer says "always re-inline". Pattern F now says to name split files by their contents.
• Evals: replaced the shallow-gate assertion and added negative assertions (no batch re-inline, sibling helpers stay extracted, no style-only edits). Added complexity_stop_when_clean.

Docs-only: no version, pin, or CHANGELOG changes.

Evidence

Blind reviews of the dogfood PRs found that fixing CC > 15 helped, but re-inlining SAFE_INLINE helpers and name-by-one-function file splits mostly hurt:

• Reduce cognitive complexity in qr_image and qr_code to <= 15 qr.dart#174, Reduce cognitive complexity across dash_discover, tool, and scripts dash_skills#59, Reduce cognitive complexity to <= 15 and de-duplicate web UI export pubviz#196, Split files over 800 lines into cohesive modules scripts.dart#147
• Restore inline _lostPoint to fix QrImage generation regression qr.dart#175 restored an inline hot kernel after the helper split made generation 39-66% slower on AOT

Related (not fixed here): #181, #183

[kevmoo]

Sanity-check pass; two optional notes inline. Looks good to land otherwise.