fix: #1547

- Fix bare import in bannerlord_harness.py
- Change 'from bannerlord_trace import' to 'from .bannerlord_trace import'
- Fixes ModuleNotFoundError when module is loaded as nexus.bannerlord_harness

Addresses issue #1547: [Tests] test_bannerlord_harness.py collection error — bare bannerlord_trace import

Error:
  ModuleNotFoundError: No module named bannerlord_trace

Fix:
  Changed from bannerlord_trace import BannerlordTraceLogger
  To from .bannerlord_trace import BannerlordTraceLogger

Verification:
- Import test passes
- All 39 bannerlord_harness tests pass (37 passed, 2 skipped)
- No collection errors

nexus/bannerlord_harness.py

@@ -29,7 +29,7 @@ from typing import Any, Callable, Optional
 
 import websockets
 
-from bannerlord_trace import BannerlordTraceLogger
+from .bannerlord_trace import BannerlordTraceLogger
 
 # ═══════════════════════════════════════════════════════════════════════════
 # CONFIGURATION