.gitignore: drop embedded worktree dirs

The parallel-agent worktrees under .claude/worktrees/ are themselves
git checkouts and were polluting commits with embedded-repo warnings.
Ignored at the top-level so they stay local-only.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: NagyVikt

.claude/worktrees/agent-a25877fd470f16da7

@@ -4,3 +4,4 @@
 .DS_Store
 dist/
 *.deb
+.claude/