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/assets/templates/references/README.md

@@ -1,39 +0,0 @@
-# references/
-
-Additional documentation agents load on demand. Files here extend SKILL.md
-without bloating its core context.
-
-## When to add a reference file
-
-The SKILL.md body carries the decision procedure only. Everything else lives
-here: lookup tables, spec restatements, output schemas, templates, example
-blocks, rationale prose, and anything only one branch reaches.
-
-Two triggers make a reference file mandatory rather than optional:
-
-- The body is over its 600-word target (900 is a hard failure), counting the
-  body only — everything after the frontmatter's closing `---`.
-- The skill has two or more mutually exclusive flows. The body then keeps only
-  a dispatch table plus the gates common to every branch, and each flow gets
-  its own self-contained file here (e.g. `create.md`, `improve.md`).
-
-## How to reference from SKILL.md
-
-Load conditionally — tell the agent exactly when to read each file:
-
-```markdown
-If the API returns a non-200 status, read `references/api-errors.md`.
-```
-
-Avoid generic "see references/ for details" — the agent loads context on
-demand, so give it a precise trigger condition.
-
-## File conventions
-
-- One topic per file — focused files mean less unnecessary context loaded
-- Kebab-case filenames (e.g. `api-errors.md`, `output-formats.md`)
-- Keep files under 200 lines where possible
-
-## If no reference files are needed
-
-Delete this README and the `references/` directory entirely.