- Add connectivity.go: BFS-based map connectivity validation with retry
- Update mapgen to use connectivity checking by default
- Add determinism_test.go: property-based tests for reproducibility
- Same seed produces identical replays
- Turn execution is deterministic
- Grid operations are deterministic
- Combat resolution is deterministic
- Full 500-turn match validation
- All 32 tests pass
- Update PROGRESS.md: Phase 1 complete
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>