docs: add new-branch-from-main rule to git guidelines

Author: KRRT7

.claude/rules/git.md

@@ -1,5 +1,6 @@
 # Git Commits & Pull Requests
 
+- **Always create a new branch from `main` before starting any new work** — never commit directly to `main` or reuse an existing feature branch for unrelated changes
 - Use conventional commit format: `fix:`, `feat:`, `refactor:`, `docs:`, `test:`, `chore:`
 - Keep commits atomic - one logical change per commit
 - Commit message body should be concise (1-2 sentences max)