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/bin/skills/diagnose/README.md

@@ -1,35 +0,0 @@
-# diagnose
-
-A six-phase discipline for hard bugs and performance regressions: feedback loop → reproduce → hypothesise → instrument → fix with a regression test → clean up.
-
-## What it does
-
-Imposes an order of operations on debugging so the agent cannot skip to guessing. The load-bearing phase is the first one: build a fast, deterministic, agent-runnable pass/fail signal for the bug. Everything downstream — bisection, hypothesis testing, instrumentation — just consumes that signal, so the skill refuses to advance to Phase 2 without one, and says so explicitly rather than hypothesising blind.
-
-The remaining phases each carry a constraint worth knowing about: hypotheses are generated 3–5 at a time and must be falsifiable, so the first plausible idea cannot anchor the whole investigation; every debug log is tagged with a unique prefix (`[DEBUG-a4f2]`) so cleanup is a single grep; the regression test is written before the fix and only at a seam that exercises the real bug pattern; and the run closes by asking what would have prevented the bug, handing off to `improve-codebase-architecture` when the answer is architectural.
-
-Performance regressions take a branch of their own inside Phase 4 — baseline measurement and bisection, not logs.
-
-## Conditional reading
-
-Neither reference file is read on every run; `SKILL.md` names the condition for each.
-
-- `references/feedback-loops.md` is read when Phase 1 has no signal yet, or when the loop you have is slow or intermittent.
-- `references/regression-seams.md` is read when Phase 5 leaves you unsure whether the available seam is deep enough — or whether one exists at all.
-
-## Usage
-
-```text
-/diagnose
-```
-
-Describe the bug or the regression. For filing and triaging a reported bug rather than diagnosing it, use `triage`; for test-first feature work, use `tdd`.
-
-## Files
-
-| File | Purpose |
-|------|---------|
-| `SKILL.md` | The six phases and their gates — what must be true before each one ends |
-| `references/feedback-loops.md` | Loaded when Phase 1 has no loop or the loop is too weak: ten ways to construct one ordered by cost, how to sharpen an existing loop, handling intermittent bugs, and what to ask the user for when the bug resists reproduction |
-| `references/regression-seams.md` | Loaded when Phase 5 is unsure about the seam: what makes a seam correct, the four shapes of a too-shallow seam, and what to do when no correct seam exists |
-| `assets/hitl-loop.template.sh` | Copy-and-edit bash template for the last-resort human-in-the-loop feedback loop, cited by `references/feedback-loops.md`. Provides `step` and `capture` helpers and prints captured values as `KEY=VALUE` for the agent to parse |