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/.apm/skills/forge/references/sources.md

@@ -28,7 +28,7 @@
 
 - **URL:** https://agentskills.io/specification.md
 - **Research doc:** plugins/kyberforge/docs/research/docs/agentskillsio/sources.md
-- **Description:** Complete SKILL.md format specification — confirms `assets/`, `references/`, and `scripts/` are warranted only by the bulk/reusability of supporting content (large reference material, executable code, templates), not by a skill's category, and forge's per-route procedures are that kind of supporting content — so the spec permits the `references/` split here but does not require it. The warrant is a house decision: ADR-0020's rule that dispatch is mandatory at two or more mutually exclusive flows, which forge's four-row table is. `references/sources.md` likewise exists for this repo's own provenance-chain convention (see `CONTEXT.md`), not because the spec requires it.
+- **Description:** Complete SKILL.md format specification — confirms `assets/`, `references/`, and `scripts/` are warranted only by the bulk/reusability of supporting content (large reference material, executable code, templates), not by a skill's category, and forge's per-route procedures are that kind of supporting content — so the spec permits the `references/` split here but does not require it. The warrant is a house decision: dispatch is mandatory at two or more mutually exclusive flows, which forge's four-row table is. `references/sources.md` likewise exists for this repo's own provenance-chain convention (see `CONTEXT.md`), not because the spec requires it.
 - **Contributing files:** SKILL.md
 - **Status:** `extracted`