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/71-dintel-brand-editor/desktop/SKILL.md

@@ -20,7 +20,7 @@ Generate brand-compliant content and evaluate existing content against the D.int
 
 - **Agent #71** — Brand Editor & Copywriter
 - **Collaborates with**: Agent #70 (Brand Guardian) for compliance review
-- **Shared constants**: `dintel-shared/src/dintel/brand.py` (colors, terminology, style tokens)
+- **Shared constants**: `_dintel-shared/src/dintel/brand.py` (colors, terminology, style tokens)
 
 ## Universal Guardrails
 
@@ -143,4 +143,4 @@ To evaluate existing content against the D.intelligence brand guide:
 
 ### Reference Files
 - **`references/dintelligence_brand_guide.md`** — Complete D.intelligence Korean writing style guide with all 12 sections: tone & voice, sentence structure, vocabulary, punctuation, content patterns, web copywriting set, and compliance checklist. Load when generating or evaluating content.
-- **`dintel-shared/src/dintel/brand.py`** — Shared brand constants (colors, terminology, style tokens) used across the Agent Corps.
+- **`_dintel-shared/src/dintel/brand.py`** — Shared brand constants (colors, terminology, style tokens) used across the Agent Corps.