chore: ignore tmpfork workspace directory (#4)

## Summary
- Add `/tmpfork/` to `.gitignore` so temporary clones/forks are never
committed.

## Validation
- `printf 'tmpfork/\ntmpfork/example.txt\n' | git check-ignore -v
--stdin`

---
_Generated with [`mux`](https://github.com/coder/mux) • Model:
`openai:gpt-5.3-codex` • Thinking: `xhigh`_

Author: ThomasK33

.gitignore

@@ -9,3 +9,6 @@
 # IDE
 .vscode/
 .idea/
+
+# Temporary external clones/forks
+/tmpfork/