test: consolidate test files into subdirectories

Move remaining top-level test files to appropriate subdirectories:
- test_system.py -> tests/sdk/
- test_system_learning.py -> tests/learning/
- test_integration*.py -> tests/integration/
- test_docker.py -> tests/deployment/
- test_rust_bridge.py -> tests/core/

Fix ROOT path in test_docker.py for new directory depth.
All 3772 tests pass, 57 skipped (optional deps).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/deployment/test_docker.py

@@ -4,7 +4,7 @@ from __future__ import annotations
 
 from pathlib import Path
 
-ROOT = Path(__file__).resolve().parent.parent
+ROOT = Path(__file__).resolve().parent.parent.parent
 DOCKER_DIR = ROOT / "deploy" / "docker"