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-security.md

@@ -0,0 +1,25 @@
+---
+allowed-tools: Bash(bash *audit_security.sh*)
+description: Security posture assessment — SIP, Gatekeeper, Firewall, FileVault, SSH, ports
+---
+
+## Your task
+
+Run a read-only security posture assessment.
+
+### Step 1 — Run the audit
+
+```bash
+bash $CLAUDE_PLUGIN_ROOT/skills/mac-optimizer/scripts/audit_security.sh
+```
+
+### Step 2 — Report
+
+Parse JSON output and present as a severity-ranked markdown table:
+
+| Severity | Finding | Recommended Action | Details |
+|---|---|---|---|
+
+### Step 3 — Guidance only
+
+The security module is **read-only**. Present findings and remediation guidance. Do NOT attempt to change security settings. Explain how the user can fix issues themselves via System Settings or Terminal commands.