docs: v3.27.3 — track Claude Code v2.1.42 + Google Antigravity section

- Claude Code releases: v2.1.41 → v2.1.42 (startup perf, prompt cache, Opus 4.6 effort callout)
- New AI ecosystem section: Google Antigravity agent-first IDE comparison
- Version sync across all docs (3.27.2 → 3.27.3)

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

README.md

@@ -6,7 +6,7 @@
 
 <p align="center">
   <a href="https://github.com/FlorianBruniaux/claude-code-ultimate-guide/stargazers"><img src="https://img.shields.io/github/stars/FlorianBruniaux/claude-code-ultimate-guide?style=for-the-badge" alt="Stars"/></a>
-  <a href="./CHANGELOG.md"><img src="https://img.shields.io/badge/Updated-Feb_15,_2026_·_v3.27.2-brightgreen?style=for-the-badge" alt="Last Update"/></a>
+  <a href="./CHANGELOG.md"><img src="https://img.shields.io/badge/Updated-Feb_16,_2026_·_v3.27.3-brightgreen?style=for-the-badge" alt="Last Update"/></a>
   <a href="./quiz/"><img src="https://img.shields.io/badge/Quiz-264_questions-orange?style=for-the-badge" alt="Quiz"/></a>
   <a href="./examples/"><img src="https://img.shields.io/badge/Templates-108-green?style=for-the-badge" alt="Templates"/></a>
   <a href="./guide/security-hardening.md"><img src="https://img.shields.io/badge/🛡️_Threat_DB-18_CVEs_·_341_malicious_skills-red?style=for-the-badge" alt="Threat Database"/></a>
@@ -746,7 +746,7 @@ See [CONTRIBUTING.md](./CONTRIBUTING.md) for guidelines.
 
 ---
 
-*Version 3.27.2 | Updated daily · Feb 15, 2026 | Crafted with Claude*
+*Version 3.27.3 | Updated daily · Feb 16, 2026 | Crafted with Claude*
 
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