feat(isolation): DynamicVRAM compatibility for process isolation

DynamicVRAM's on-demand model loading/offloading conflicted with  process isolation in three ways: RPC tensor transport stalls from mid-call GPU offload, race conditions between model lifecycle and active RPC operations, and false positive memory leak detection from changed finalizer patterns.

- Marshal CUDA tensors to CPU before RPC transport for dynamic models
- Add operation state tracking + quiescence waits at workflow boundaries
- Distinguish proxy reference release from actual leaks in cleanup_models_gc
- Fix init order: DynamicVRAM must initialize before isolation proxies
- Add RPC timeouts to prevent indefinite hangs on model unavailability
- Prevent proxy-of-proxy chains from DynamicVRAM model reload cycles
- Add torch.device/torch.dtype serializers for new DynamicVRAM RPC paths
- Guard isolation overhead so non-isolated workflows are unaffected
- Migrate env var to PYISOLATE_CHILD

utils/install_util.py

@@ -1,5 +1,7 @@
 from pathlib import Path
 import sys
+import logging
+import re
 
 # The path to the requirements.txt file
 requirements_path = Path(__file__).parents[1] / "requirements.txt"
@@ -16,3 +18,34 @@ Please install the updated requirements.txt file by running:
 {sys.executable} {extra}-m pip install -r {requirements_path}
 If you are on the portable package you can run: update\\update_comfyui.bat to solve this problem.
 """.strip()
+
+
+def is_valid_version(version: str) -> bool:
+    """Validate if a string is a valid semantic version (X.Y.Z format)."""
+    pattern = r"^(\d+)\.(\d+)\.(\d+)$"
+    return bool(re.match(pattern, version))
+
+
+PACKAGE_VERSIONS = {}
+def get_required_packages_versions():
+    if len(PACKAGE_VERSIONS) > 0:
+        return PACKAGE_VERSIONS.copy()
+    out = PACKAGE_VERSIONS
+    try:
+        with open(requirements_path, "r", encoding="utf-8") as f:
+            for line in f:
+                line = line.strip().replace(">=", "==")
+                s = line.split("==")
+                if len(s) == 2:
+                    version_str = s[-1]
+                    if not is_valid_version(version_str):
+                        logging.error(f"Invalid version format in requirements.txt: {version_str}")
+                        continue
+                    out[s[0]] = version_str
+        return out.copy()
+    except FileNotFoundError:
+        logging.error("requirements.txt not found.")
+        return None
+    except Exception as e:
+        logging.error(f"Error reading requirements.txt: {e}")
+        return None