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/git/.apm/skills/git-commits/SKILL.md

@@ -8,7 +8,7 @@ description: >
   Not branch lifecycle -> `git-branches`.
 
 metadata:
-  version: "0.1.4"
+  version: "0.1.5"
   category: git
   source_keys:
     - conventional-commits-spec
@@ -21,7 +21,7 @@ allowed-tools: Bash
 
 ## Gotchas
 
-- **Run git as `rtk git <subcommand>`, never bare `git`** — org convention, in `&&` chains too. Exceptions: ADR-0023 clause 3.
+- **Run git as `rtk git <subcommand>`, never bare `git`** — org convention, in `&&` chains too, except where a skill's Gotchas name a specific bare-git case (interactive rebase here).
 - **Refuse to force-push `main`/`master`** — a rewrite leaves the branch diverged and the reflex is to force it back; safe only where nobody else has based work on it.
 - **`reset --hard` is a confirmation gate, not a default.** It overwrites the working tree, and uncommitted edits it discards were never in git, so no reflog recovers them. Name what will be lost and offer a stash first.
 - **Never add `--no-verify`** — using it when a hook fails bypasses the QA gate the pipeline depends on. Only on the user's explicit demand, with a warning.