● 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_policy_priority.py

@@ -0,0 +1,180 @@
+"""
+Test policy priority and conflicts (Priority 2)
+
+Tests that user policies override base policies correctly
+"""
+
+import json
+import subprocess
+from pathlib import Path
+
+import pytest
+
+
+@pytest.fixture
+def conflicting_policies(temp_policy_dir, temp_user_policy_dir):
+    """Create conflicting base and user policies"""
+    # Base policy
+    base_content = {
+        "numpy": {
+            "apply_first_match": [
+                {
+                    "type": "skip",
+                    "reason": "Base policy skip"
+                }
+            ]
+        }
+    }
+    base_file = temp_policy_dir / "pip-policy.json"
+    base_file.write_text(json.dumps(base_content, indent=2))
+
+    # User policy (should override)
+    user_content = {
+        "numpy": {
+            "apply_first_match": [
+                {
+                    "type": "force_version",
+                    "version": "1.26.0",
+                    "reason": "User override"
+                }
+            ]
+        }
+    }
+    user_file = temp_user_policy_dir / "pip-policy.user.json"
+    user_file.write_text(json.dumps(user_content, indent=2))
+
+    return base_file, user_file
+
+
+@pytest.mark.unit
+def test_user_policy_overrides_base_policy(
+    conflicting_policies,
+    mock_manager_util,
+    mock_context,
+    mock_subprocess_success
+):
+    """
+    Test user policy completely replaces base policy
+
+    Priority: 2 (Important)
+
+    Purpose:
+        Verify that user policy completely overrides base policy
+        at the package level (not section-level merge).
+    """
+    import sys
+    # Path setup handled by conftest.py
+
+    from comfyui_manager.common.pip_util import get_pip_policy
+
+    policy = get_pip_policy()
+
+    # Verify user policy replaced base policy
+    assert "numpy" in policy
+    assert "apply_first_match" in policy["numpy"]
+    assert len(policy["numpy"]["apply_first_match"]) == 1
+
+    # Should be force_version (user), not skip (base)
+    assert policy["numpy"]["apply_first_match"][0]["type"] == "force_version"
+    assert policy["numpy"]["apply_first_match"][0]["version"] == "1.26.0"
+
+    # Base policy skip should be completely gone
+    assert not any(
+        item["type"] == "skip"
+        for item in policy["numpy"]["apply_first_match"]
+    )
+
+
+@pytest.fixture
+def first_match_policy(temp_policy_dir):
+    """Create policy with multiple apply_first_match entries"""
+    policy_content = {
+        "pkg": {
+            "apply_first_match": [
+                {
+                    "condition": {
+                        "type": "installed",
+                        "package": "numpy"
+                    },
+                    "type": "force_version",
+                    "version": "1.0"
+                },
+                {
+                    "type": "force_version",
+                    "version": "2.0"
+                },
+                {
+                    "type": "skip"
+                }
+            ]
+        }
+    }
+
+    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_first_match_subprocess(monkeypatch):
+    """Mock subprocess for first match test"""
+    call_sequence = []
+
+    installed_packages = {
+        "numpy": "1.26.0"
+    }
+
+    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 and "pkg" in cmd:
+            if "pkg==1.0" in cmd:
+                installed_packages["pkg"] = "1.0"
+            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_first_match_stops_at_first_satisfied(
+    first_match_policy,
+    mock_manager_util,
+    mock_context,
+    mock_first_match_subprocess
+):
+    """
+    Test apply_first_match stops at first satisfied condition
+
+    Priority: 2 (Important)
+
+    Purpose:
+        Verify that in apply_first_match, only the first policy
+        with a satisfied condition is executed (exclusive execution).
+    """
+    import sys
+    # Path setup handled by conftest.py
+
+    from comfyui_manager.common.pip_util import PipBatch
+
+    call_sequence, installed_packages = mock_first_match_subprocess
+
+    with PipBatch() as batch:
+        result = batch.install("pkg")
+
+    # Verify installation succeeded
+    assert result is True
+
+    # First condition satisfied (numpy installed), so version 1.0 applied
+    install_calls = [cmd for cmd in call_sequence if "install" in cmd and "pkg" in cmd]
+    assert len(install_calls) > 0
+    assert "pkg==1.0" in install_calls[0]
+    assert "pkg==2.0" not in str(call_sequence)  # Second policy not applied