feat(isolation): process isolation for custom nodes via pyisolate

Adds opt-in process isolation for custom nodes using pyisolate's
bwrap sandbox and JSON-RPC bridge. Each isolated node pack runs in
its own child process with zero-copy tensor transfer via shared memory.

Core infrastructure:
- CLI flag --use-process-isolation to enable isolation
- Host/child startup fencing via PYISOLATE_CHILD env var
- Manifest-driven node discovery and extension loading
- JSON-RPC bridge between host and child processes
- Shared memory forensics for leak detection

Proxy layer:
- ModelPatcher, CLIP, VAE, and ModelSampling proxies
- Host service proxies (folder_paths, model_management, progress, etc.)
- Proxy base with automatic method forwarding

Execution integration:
- Extension wrapper with V3 hidden param mapping
- Runtime helpers for isolated node execution
- Host policy for node isolation decisions
- Fenced sampler device handling and model ejection parity

Serializers for cross-process data transfer:
- File3D (GLB), PLY (structured + gaussian), NPZ (streaming frames),
  VIDEO (VideoFromFile + VideoFromComponents) serializers
- data_type flag in SerializerRegistry for type-aware dispatch
- Isolated get_temp_directory() fence

New core save nodes:
- SavePLY and SaveNPZ with comfytype registrations (Ply, Npz)

DynamicVRAM compatibility:
- comfy-aimdo early init gated by isolation fence

Tests:
- Integration and policy tests for isolation lifecycle
- Manifest loader, host policy, proxy, and adapter unit tests

Depends on: pyisolate >= 0.9.2

comfy_api/latest/_io.py

@@ -27,7 +27,7 @@ if TYPE_CHECKING:
 from comfy_api.internal import (_ComfyNodeInternal, _NodeOutputInternal, classproperty, copy_class, first_real_override, is_class,
     prune_dict, shallow_clone_class)
 from comfy_execution.graph_utils import ExecutionBlocker
-from ._util import MESH, VOXEL, SVG as _SVG, File3D
+from ._util import MESH, VOXEL, SVG as _SVG, File3D, PLY as _PLY, NPZ as _NPZ
 
 
 class FolderType(str, Enum):
@@ -678,6 +678,16 @@ class Mesh(ComfyTypeIO):
     Type = MESH
 
 
+@comfytype(io_type="PLY")
+class Ply(ComfyTypeIO):
+    Type = _PLY
+
+
+@comfytype(io_type="NPZ")
+class Npz(ComfyTypeIO):
+    Type = _NPZ
+
+
 @comfytype(io_type="FILE_3D")
 class File3DAny(ComfyTypeIO):
     """General 3D file type - accepts any supported 3D format."""
@@ -2197,6 +2207,8 @@ __all__ = [
     "LossMap",
     "Voxel",
     "Mesh",
+    "Ply",
+    "Npz",
     "File3DAny",
     "File3DGLB",
     "File3DGLTF",