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/75-dintel-marketing-mgr/README.md

@@ -1,6 +1,6 @@
 # 75 — D.intelligence Marketing Manager
 
-**Agent #75** in the [D.intelligence Agent Corps](../../dintel-shared/README.md).
+**Agent #75** in the [D.intelligence Agent Corps](../../_dintel-shared/README.md).
 Marketing content pipeline management for [D.intelligence](https://dintelligence.co.kr).
 
 ## What It Does
@@ -20,9 +20,9 @@ Marketing content pipeline management for [D.intelligence](https://dintelligence
 | Skill Name | `dintel-marketing-mgr` |
 | Version | 1.0.0 |
 | Autonomy | **Draft & Wait** — drafts content, waits for Andrew's approval before publishing |
-| Collaborates With | **#71 Brand Editor** (writing check), **#70 Brand Guardian** (compliance review), **dintel-shared** (shared constants) |
+| Collaborates With | **#71 Brand Editor** (writing check), **#70 Brand Guardian** (compliance review), **_dintel-shared** (shared constants) |
 
-This agent uses shared brand constants from `dintel-shared/src/dintel/brand.py` for colors, terminology, and style rules.
+This agent uses shared brand constants from `_dintel-shared/src/dintel/brand.py` for colors, terminology, and style rules.
 
 ## Content Pipeline (Chain C)