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/81-mac-optimizer/commands/mac-environment.md

@@ -0,0 +1,30 @@
+---
+allowed-tools: Bash(bash *audit_environment.sh*), Bash(echo *), Bash(cp *)
+description: Audit shell environment — PATH, symlinks, shell configs, and startup time
+---
+
+## Your task
+
+Audit the shell environment on this Mac.
+
+### Step 1 — Run the audit
+
+```bash
+bash $CLAUDE_PLUGIN_ROOT/skills/mac-optimizer/scripts/audit_environment.sh
+```
+
+### Step 2 — Report
+
+Parse JSON output and present as a severity-ranked markdown table:
+
+| Severity | Finding | Recommended Action | Details |
+|---|---|---|---|
+
+### Step 3 — Ask for consent
+
+If there are fixable issues (duplicate PATH entries, broken symlinks, non-existent directories), list them and ask which to fix.
+
+### Safety rules
+
+- Back up shell configs before modifying: `cp ~/.zshrc ~/.config/mac-optimizer-backups/.zshrc.$(date +%s)`
+- Present PATH consolidation suggestions but don't auto-modify