● feat: Draft pip package policy management system (not yet integrated)

Add comprehensive pip dependency conflict resolution framework as draft implementation. This is self-contained and does not affect existing
ComfyUI Manager functionality.

Key components:
- pip_util.py with PipBatch class for policy-driven package management
- Lazy-loaded policy system supporting base + user overrides
- Multi-stage policy execution (uninstall → apply_first_match → apply_all_matches → restore)
- Conditional policies based on platform, installed packages, and ComfyUI version
- Comprehensive test suite covering edge cases, workflows, and platform scenarios
- Design and implementation documentation

Policy capabilities (draft):
- Package replacement (e.g., PIL → Pillow, opencv-python → opencv-contrib-python)
- Version pinning to prevent dependency conflicts
- Dependency protection during installations
- Platform-specific handling (Linux/Windows, GPU detection)
- Pre-removal and post-restoration workflows

Testing infrastructure:
- Pytest-based test suite with isolated environments
- Dependency analysis tools for conflict detection
- Coverage for policy priority, edge cases, and environment recovery

Status: Draft implementation complete, integration with manager workflows pending.

tests/requirements.txt

@@ -0,0 +1,19 @@
+# Test Dependencies for pip_util.py
+# Install in isolated venv to prevent environment corruption
+
+# Testing Framework
+pytest>=7.4.0
+pytest-cov>=4.1.0
+pytest-mock>=3.11.0
+
+# Code Quality
+flake8>=6.0.0
+black>=23.0.0
+mypy>=1.5.0
+
+# Dependencies from main project
+packaging>=23.0
+
+# Mock and testing utilities
+responses>=0.23.0
+freezegun>=1.2.0