release: v2.1.2 — landing page TSX output, brand voice integration, docs update

- Landing page generator defaults to Next.js TSX + Tailwind CSS (4 design styles)
- Brand voice analyzer integrated into landing page generation workflow
- CHANGELOG, CLAUDE.md, README.md updated for v2.1.2
- All 13 plugin.json + marketplace.json bumped to 2.1.2
- Gemini/Codex skill indexes re-synced
- Backward compatible: --format html preserved, no breaking changes

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

c-level-advisor/.claude-plugin/plugin.json

@@ -1,7 +1,7 @@
 {
   "name": "c-level-skills",
   "description": "28 C-level advisory skills: complete virtual board of directors with CEO, CTO, COO, CPO, CMO, CFO, CRO, CISO, CHRO advisors, executive mentor, founder coach, Chief of Staff router, board meetings, decision logger, board deck builder, scenario war room, competitive intel, org health diagnostic, M&A playbook, international expansion, culture architect, change management, strategic alignment, and more",
-  "version": "2.1.1",
+  "version": "2.1.2",
   "author": {
     "name": "Alireza Rezvani",
     "url": "https://alirezarezvani.com"