docs: trim skill READMEs and ADR/changelog narration

Two related simplification-audit findings, bundled because they edit
some of the same skill-audit files and splitting would fragment
single-file diffs.

Finding 10: delete 48 per-skill/reference README.md files (they
restated SKILL.md in narrative form and no agent ever loads them) plus
2 scaffold templates. Drop the README criterion from skill-audit's
file-structure.md and finding-criteria.md, and the README-generation
step from skill-author's new-skill.sh; update new-skill.bats to match.
Plugin-root READMEs are kept intentionally, out of scope.

Finding 12: strip historical ADR-0020/ADR-0023 citations and
changelog-style narration from model-facing skill content across
kyberforge and git plugin skills. Delete skill-author's one-time
retrofit.md migration guide and its references. Some ADR-0023 tags
were not narration but check-rtk-prefix's required opt-out marker for
intentionally-bare git commands -- those were restored, not stripped.

Mirror re-synced and full pre-commit/pre-push suite verified green.

Refs: SIMPLIFICATION-AUDIT.md findings 10, 12

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YR2CjVumUbEGWcMikcoXBD

plugins/kyberforge/skills/skill-author/references/improve.md

@@ -71,23 +71,16 @@ outperforms an exhaustive one.
 writing a rule in all caps (ALWAYS/NEVER), reframe it: explain why the behavior matters so the
 agent can apply judgment in edge cases.
 
-**Retrofit before extending.** Any edit to a skill that predates ADR-0020 has to bring it into the
-contract first — the gates are hot and carry no baseline file, so a one-line fix to a
+**Retrofit before extending.** Any edit to a skill that does not meet the contract has to bring it
+into compliance first — the gates are hot and carry no baseline file, so a one-line fix to a
 non-compliant skill cannot be committed until the description and body meet
 `references/contract.md`. Treat that retrofit as part of the same change, not a follow-up.
 
-If the skill's description exceeds 250 characters, or its body-only word count exceeds 600, read
-`references/retrofit.md` before editing. It carries the ordered cut procedure, the
-mutually-exclusive-flows test, the reference-file conventions this flow needs, the collateral
-checklist for `README.md` and `references/sources.md`, and a worked description retrofit. Do not
-improvise the cuts — four dry runs invented six to ten different answers to the same questions.
-
 If a signal points to a script or reference file, edit that file directly rather than adding a
 workaround in SKILL.md.
 
 **A skill carrying no `metadata.version` is seeded at `"1.0.0"`, not bumped** — `SKILL.md` Step 4's
 patch bump presumes a version to bump, and ADR-0022 reserves `"0.1.0"` for a newly created skill.
-`references/retrofit.md` carries the reasoning.
 
 **Check for regressions before handing back.** `SKILL.md` Step 4 tells you to resolve every FAIL,
 which says nothing about a check that passed *before* these edits and no longer does. Compare the