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/80-claude-settings-optimizer/code/scripts/requirements.txt

@@ -0,0 +1,7 @@
+# Claude Code Settings Optimizer
+# No external dependencies - uses only Python standard library
+# json, sys, pathlib are built-in
+
+# Optional: For future enhancements
+# pyyaml>=6.0        # YAML parsing for MCP configs
+# rich>=13.0         # Better terminal output