refactor: reorganize skill numbering, remove obsolete skills, rename shared libs

- Rename: 00→80 claude-settings-optimizer, 88→79 dintel-skill-update,
  92→81 mac-optimizer, 93→82 tui-design-template
- Rename: dintel-shared → _dintel-shared (consistent with _ourdigital-shared)
- Remove: 61-gtm-manager, 62-gtm-guardian (obsolete), 99_archive
- Update all dintel-* skill refs (114 occurrences across 31 files)
- Sync README.md, CLAUDE.md, AGENTS.md with new structure

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

custom-skills/72-dintel-doc-secretary/desktop/SKILL.md

@@ -291,7 +291,7 @@ D.intelligence가 생산하는 모든 문서 — 회의록, 리포트, 제안서
 ### Step 5: Finalize (After Approval)
 - Remove `[DRAFT - Awaiting Review]` watermark
 - Apply final formatting adjustments per Andrew's feedback
-- If DOCX/PPTX output needed, use `dintel-shared` document generation utilities
+- If DOCX/PPTX output needed, use `_dintel-shared` document generation utilities
 - Hand off to Brand Editor (#71) and Brand Guardian (#70) for review chain
 
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