refactor(debugging): rename diagnose skill to debug

[kyle-sexton]

What

Renames the debugging plugin's sole skill: /debugging:diagnose → /debugging:debug. One atomic rename PR per the shadowed-skill-renames contract (#256): directory (git mv) and frontmatter name move together, and all repo-wide references update in the same PR.

• plugins/debugging/skills/diagnose/ → plugins/debugging/skills/debug/ (all bundled files)
• Frontmatter name: debug; description unchanged — already third-person what+when, and keeps "diagnose this" as a trigger phrase
• Internal ${CLAUDE_PLUGIN_ROOT}/skills/diagnose/... paths, self-references, checklist/reference headers, and evals updated
• plugins/debugging/README.md invocation line updated
• plugins/verification/skills/confirm/evals/evals.json boundary notes updated
• docs/MIGRATION-PLAYBOOK.md non-router-skill example updated
• plugins/debugging bumped 0.3.0 → 0.4.0 (0.x breaking-by-minor precedent); new CHANGELOG.md with the breaking entry

Why

The skill runs the full repro → hypothesize → fix → regression-test loop; "diagnose" promised only the first half, and twinned confusingly with the unrelated /testing:diagnose (a read-only test-failure investigator that keeps its name). Pre-migration shadow-compromise naming is no longer needed now that plugin namespacing exists.

Breaking change

• /debugging:diagnose no longer resolves; invoke /debugging:debug. Clean break — no renames-map entry per the contract (marketplace renames map unchanged; its existing "diagnose": "debugging" entry is the historical plugin-level rename).
• No collision with Claude Code's built-in bundled /debug skill: plugin skills have no bare command form, so the plugin skill is only reachable as the namespaced /debugging:debug.

Deliberate skips

• plugins/testing/** — /testing:diagnose is a different skill and keeps its name.
• docs/topics/plugin-organization/PLAN.md — historical record of the earlier plugin reorganization (its D3/D13 rows describe decisions as made at the time).
• .claude-plugin/marketplace.json — renames map untouched (contract constraint); the diagnose tag stays as a discovery keyword, mirroring the retained trigger word.
• plugin.json keywords keeps diagnose as a discovery keyword.

Verification

• git grep -n "debugging:diagnose" → 0 hits
• git grep -n "skills/diagnose" → 0 hits
• git grep -nE "(^|[^a-z:])/diagnose\b" → 0 hits
• Remaining diagnose hits in plugins/debugging are the deliberate trigger word in the skill description and the plugin keyword
• Edited JSON files parse cleanly

🤖 Generated with Claude Code

https://claude.ai/code/session_01YVApnNGoKxYMJKNQx1QK8C

Related

No linked issue. Contract source: #256. Sibling shadowed-skill rename PRs: #269, #270, #271.

[claude]

Claude finished @kyle-sexton's task in 2m 20s —— View job

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PR Review: refactor(debugging): rename diagnose skill to debug

• Gather context and understand request
• Review changed files
  • plugins/debugging/skills/debug/SKILL.md
  • plugins/debugging/skills/debug/evals/evals.json
  • plugins/debugging/skills/debug/reference/ecosystem-debugging.md
  • plugins/debugging/skills/debug/templates/checklist.md
  • plugins/debugging/.claude-plugin/plugin.json
  • plugins/debugging/CHANGELOG.md
  • plugins/debugging/README.md
  • plugins/verification/skills/confirm/evals/evals.json
  • docs/MIGRATION-PLAYBOOK.md
• Verify no stale references remain
• Post review

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This is a clean, well-scoped atomic rename. The core contract — directory + frontmatter move together, discovery keywords and trigger phrases preserved, cross-plugin references swept — is satisfied. I independently verified the claimed greps: debugging:diagnose has zero hits outside of the CHANGELOG (which is the correct historical record), and skills/diagnose has zero hits. One minor finding below.

Finding: CHANGELOG.md missing date in version header

File: plugins/debugging/CHANGELOG.md, line 6

The file declares it follows Keep a Changelog 1.1.0, which specifies the version header format as ## [version] - YYYY-MM-DD. The entry reads ## [0.4.0] with no date, which is a spec deviation — a consumer scanning the changelog won't know when the breaking change shipped.

-## [0.4.0]
+## [0.4.0] - 2026-07-17

Fix this →

Everything else looks correct

• Internal ${CLAUDE_PLUGIN_ROOT} paths — all updated from skills/diagnose/ to skills/debug/ across SKILL.md, checklist.md, ecosystem-debugging.md, and the HITL script reference. ✓
• Frontmatter — name: debug, argument-hint example, and self-reference in the skill body all updated. ✓
• Evals — skill_name: "debug" and all six eval prompts use /debugging:debug. ✓
• Cross-plugin reference — verification/skills/confirm/evals/evals.json eval id 3 correctly routes to /debugging:debug in both expected_output and expectations. ✓
• MIGRATION-PLAYBOOK.md — the non-router-skill example (e.g. \debug`) correctly replaced from diagnose`. ✓
• Version bump — 0.3.0 → 0.4.0 is correct under the 0.x breaking-by-minor precedent. ✓
• diagnose retained as discovery keyword — plugin.json keywords and the skill description trigger phrase preserved intentionally. ✓
• Deliberate skips — marketplace renames map, plugin.json keywords, PLAN.md historical record, and plugins/testing/** are all correct non-touches. ✓

One non-blocking minor: the CHANGELOG date. Otherwise approve-ready.