docs: clean up public repo — remove IDE files, fix stale refs

- Untrack .claude/commands/ and .windsurf/workflows/ (personal IDE config)
- Fix .gitignore: scope /CLAUDE.md to root only, add .claude/, remove
  incorrect .github/workflows/ exclusion (CI needs these tracked)
- Rename docs/ANTIGRAVITY.md → docs/CLAUDE.md (Claude Desktop setup;
  "Antigravity" was an internal codename, confusing to public users)
- Fix stale repo name: masdevid/mt5-mcp → masdevid/mt5-quant in
  README.md, docs/CLAUDE.md, CURSOR.md, QUICKSTART.md, VSCODE.md, WINDSURF.md

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

.gitignore

@@ -20,14 +20,12 @@ config/baseline.json
 config/backtest_history.json
 
 # Claude Code (personal, not for repo)
-CLAUDE.md
+/CLAUDE.md
+.claude/
 
 # Windsurf (local workflows, not for repo)
 .windsurf/
 
-# GitHub Actions (local workflows, not for repo)
-.github/workflows/
-
 # macOS
 .DS_Store