feat: scaffold avatar pipeline with ComfyUI driver, MLflow logging, and rclone promotion

- setup.sh: automated desktop env setup (ComfyUI, 3D-Pack, UniRig, Blender, Ray)
- ray-join.sh: join Ray cluster as external worker with 3d_gen resource label
- vrm_export.py: headless Blender GLB→VRM conversion script
- generate.py: ComfyUI API driver (submit workflow JSON, poll, download outputs)
- log_mlflow.py: REST-only MLflow experiment tracking (no SDK dependency)
- promote.py: rclone promotion of VRM files to gravenhollow S3
- CLI entry points: avatar-generate, avatar-promote
- workflows/ placeholder for ComfyUI exported workflow JSONs

Implements ADR-0063 (ComfyUI + TRELLIS + UniRig 3D avatar pipeline)

scripts/vrm_export.py

@@ -0,0 +1,111 @@
+#!/usr/bin/env python3
+"""Headless Blender script for GLB → VRM conversion.
+
+Invoked via:
+    blender --background --python scripts/vrm_export.py -- \\
+        --input rigged_model.glb \\
+        --output avatar.vrm \\
+        --name "Avatar Name" \\
+        --author "DaviesTechLabs Pipeline"
+
+Requires:
+    - Blender 4.x
+    - VRM Add-on for Blender (https://vrm-addon-for-blender.info/en/)
+"""
+
+import argparse
+import sys
+
+# Blender's bpy is only available when running inside Blender
+try:
+    import bpy  # type: ignore[import-untyped]
+except ImportError:
+    print("ERROR: This script must be run inside Blender.")
+    print("Usage: blender --background --python scripts/vrm_export.py -- --input model.glb --output model.vrm")
+    sys.exit(1)
+
+
+def parse_args() -> argparse.Namespace:
+    """Parse arguments after the '--' separator in Blender CLI."""
+    argv = sys.argv[sys.argv.index("--") + 1 :] if "--" in sys.argv else []
+    parser = argparse.ArgumentParser(description="Convert rigged GLB to VRM")
+    parser.add_argument("--input", required=True, help="Path to rigged GLB file")
+    parser.add_argument("--output", required=True, help="Output VRM file path")
+    parser.add_argument("--name", default="Generated Avatar", help="Avatar display name")
+    parser.add_argument("--author", default="DaviesTechLabs Pipeline", help="Author name")
+    return parser.parse_args(argv)
+
+
+def clear_scene() -> None:
+    """Remove all objects from the scene."""
+    bpy.ops.wm.read_factory_settings(use_empty=True)
+
+
+def import_glb(path: str) -> None:
+    """Import a GLB file into the current scene."""
+    bpy.ops.import_scene.gltf(filepath=path)
+    print(f"Imported: {path}")
+    print(f"  Objects: {[obj.name for obj in bpy.data.objects]}")
+
+
+def find_armature() -> "bpy.types.Object":
+    """Find the armature object in the scene."""
+    armatures = [obj for obj in bpy.data.objects if obj.type == "ARMATURE"]
+    if not armatures:
+        print("ERROR: No armature found in imported model.")
+        print("  Available objects:", [obj.name for obj in bpy.data.objects])
+        sys.exit(1)
+    if len(armatures) > 1:
+        print(f"WARNING: Multiple armatures found, using first: {armatures[0].name}")
+    return armatures[0]
+
+
+def configure_vrm_metadata(armature: "bpy.types.Object", name: str, author: str) -> None:
+    """Set VRM 1.0 metadata on the armature."""
+    # The VRM Add-on stores metadata as a custom property
+    armature["vrm_addon_extension"] = {
+        "spec_version": "1.0",
+        "vrm0": {
+            "meta": {
+                "title": name,
+                "author": author,
+                "allowedUserName": "Everyone",
+                "violentUsageName": "Disallow",
+                "sexualUsageName": "Disallow",
+                "commercialUsageName": "Allow",
+                "licenseName": "MIT",
+            }
+        },
+    }
+    print(f"  VRM metadata: name={name}, author={author}")
+
+
+def export_vrm(path: str) -> None:
+    """Export the scene as VRM."""
+    bpy.ops.export_scene.vrm(filepath=path)
+    print(f"Exported VRM: {path}")
+
+
+def main() -> None:
+    args = parse_args()
+
+    print(f"Converting GLB to VRM:")
+    print(f"  Input:  {args.input}")
+    print(f"  Output: {args.output}")
+    print(f"  Name:   {args.name}")
+
+    clear_scene()
+    import_glb(args.input)
+
+    armature = find_armature()
+    bpy.context.view_layer.objects.active = armature
+    armature.select_set(True)
+
+    configure_vrm_metadata(armature, args.name, args.author)
+    export_vrm(args.output)
+
+    print("Done.")
+
+
+if __name__ == "__main__":
+    main()