Add SE workflow temp files to .gitignore

## Summary
Add gitignore patterns for SE workflow temporary files (proactive - before any get tracked).

## Patterns to add to .gitignore
```
# SE workflow temporary files
tests/TEST-CASES-*.md
tests/TEST-RESULTS-*.md
IMPLEMENTATION-*.md
*-review.md
```

## Acceptance Criteria
- [ ] Patterns added to .gitignore
- [ ] Future SE workflow files auto-ignored