Add .claude/ to .gitignore

Excludes Claude user configuration directory from version control.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

Author: nikomatsakis

.gitignore

@@ -18,3 +18,6 @@ extension/*.vsix
 .fastembed_cache/
 
 .socratic-shell-review.json
+
+# Claude user configuration directory
+.claude/