● 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/common/pip_util/test_platform_conditions.py

@@ -0,0 +1,139 @@
+"""
+Test platform-specific conditions (Priority 2)
+
+Tests OS and GPU detection for conditional policies
+"""
+
+import json
+import subprocess
+from pathlib import Path
+
+import pytest
+
+
+@pytest.fixture
+def platform_policy(temp_policy_dir):
+    """Create policy with platform conditions"""
+    policy_content = {
+        "onnxruntime": {
+            "apply_first_match": [
+                {
+                    "condition": {
+                        "type": "platform",
+                        "os": "linux",
+                        "has_gpu": True
+                    },
+                    "type": "replace",
+                    "replacement": "onnxruntime-gpu"
+                }
+            ]
+        }
+    }
+
+    policy_file = temp_policy_dir / "pip-policy.json"
+    policy_file.write_text(json.dumps(policy_content, indent=2))
+    return policy_file
+
+
+@pytest.fixture
+def mock_platform_subprocess(monkeypatch):
+    """Mock subprocess for platform test"""
+    call_sequence = []
+    installed_packages = {}
+
+    def mock_run(cmd, **kwargs):
+        call_sequence.append(cmd)
+
+        # pip freeze
+        if "freeze" in cmd:
+            output = "\n".join([f"{pkg}=={ver}" for pkg, ver in installed_packages.items()])
+            return subprocess.CompletedProcess(cmd, 0, output, "")
+
+        # pip install
+        if "install" in cmd:
+            if "onnxruntime-gpu" in cmd:
+                installed_packages["onnxruntime-gpu"] = "1.0.0"
+            elif "onnxruntime" in cmd:
+                installed_packages["onnxruntime"] = "1.0.0"
+            return subprocess.CompletedProcess(cmd, 0, "", "")
+
+        return subprocess.CompletedProcess(cmd, 0, "", "")
+
+    monkeypatch.setattr("subprocess.run", mock_run)
+    return call_sequence, installed_packages
+
+
+@pytest.mark.integration
+def test_linux_gpu_uses_gpu_package(
+    platform_policy,
+    mock_manager_util,
+    mock_context,
+    mock_platform_subprocess,
+    mock_platform_linux,
+    mock_torch_cuda_available
+):
+    """
+    Test GPU-specific package on Linux + GPU
+
+    Priority: 2 (Important)
+
+    Purpose:
+        Verify that platform-conditional policies correctly detect
+        Linux + GPU and install the appropriate package variant.
+    """
+    import sys
+    # Path setup handled by conftest.py
+
+    from comfyui_manager.common.pip_util import PipBatch
+
+    call_sequence, installed_packages = mock_platform_subprocess
+
+    with PipBatch() as batch:
+        result = batch.install("onnxruntime")
+
+    # Verify installation succeeded
+    assert result is True
+
+    # Verify GPU version was installed
+    install_calls = [cmd for cmd in call_sequence if "install" in cmd]
+    assert any("onnxruntime-gpu" in str(cmd) for cmd in install_calls)
+    assert "onnxruntime-gpu" in installed_packages
+
+
+@pytest.mark.integration
+def test_windows_no_gpu_uses_cpu_package(
+    platform_policy,
+    mock_manager_util,
+    mock_context,
+    mock_platform_subprocess,
+    mock_platform_windows,
+    mock_torch_cuda_unavailable
+):
+    """
+    Test CPU package on Windows + No GPU
+
+    Priority: 2 (Important)
+
+    Purpose:
+        Verify that when platform conditions are not met,
+        the original package is installed without replacement.
+    """
+    import sys
+    # Path setup handled by conftest.py
+
+    from comfyui_manager.common.pip_util import PipBatch
+
+    call_sequence, installed_packages = mock_platform_subprocess
+
+    with PipBatch() as batch:
+        result = batch.install("onnxruntime")
+
+    # Verify installation succeeded
+    assert result is True
+
+    # Verify CPU version was installed (no GPU replacement)
+    install_calls = [cmd for cmd in call_sequence if "install" in cmd]
+    assert any("onnxruntime" in str(cmd) for cmd in install_calls)
+    assert "onnxruntime-gpu" not in str(call_sequence)
+    assert "onnxruntime" in installed_packages
+    assert "onnxruntime-gpu" not in installed_packages