update CLAUDE.md with separate commit guidance

Add critical note that each commit should address ONE specific fix or feature.
Multiple unrelated changes should be committed separately for clearer history.

CLAUDE.md

···
 - Use concise summary line describing the change
 - Add additional details if needed, but keep it focused
 
+**CRITICAL: Commit separate concerns separately**
+- Each commit should address ONE specific fix or feature
+- DO NOT bundle multiple unrelated changes into a single commit
+- If fixing multiple bugs, create separate commits for each bug fix
+- Example: Login typeahead fix, card spacing fix, and toast refactor = 3 commits
+
 **Example:**
 ```bash
 git commit -m "remove deprecated 'followed' field and cleanup codebase