feat: Add VRM Blender addon with complete import/export functionality

- Add core VRM addon infrastructure with manifest and registration
- Add common utilities module with file system, logging, and conversion helpers
- Add human bone mapper with support for multiple rigging standards (Mixamo, MMD, Unreal, Rigify, etc.)
- Add VRM 0.x and 1.x format support with property groups and handlers
- Add editor UI panels for VRM metadata, spring bones, and MToon materials
- Add exporter with glTF2 extension support for VRM format serialization
- Add importer with scene reconstruction and armature generation
- Add MToon shader support with auto-setup and material migration
- Add spring bone physics simulation with constraint handling
- Add node constraint editor for advanced rigging control
- Add comprehensive validation and error handling with user dialogs
- Add scene watcher for real-time property synchronization
- Add workspace management and preference system
- Include Python cache files and Blender manifest configuration
- This is the initial commit establishing the complete VRM addon ecosystem for Blender

common/debug.py

@@ -0,0 +1,60 @@
+# SPDX-License-Identifier: MIT OR GPL-3.0-or-later
+import math
+from collections.abc import Sequence
+from typing import Union
+
+from mathutils import Matrix, Quaternion, Vector
+
+
+def dump(v: Union[Matrix, Vector, Quaternion, float]) -> str:
+    if isinstance(v, (float, int)):
+        return str(v)
+
+    if isinstance(v, Matrix):
+        t, r, s = v.decompose()
+        return f"Matrix(T={dump(t)},R={dump(r)},S={dump(s)})"
+
+    if isinstance(v, Vector):
+        return f"({v.x:.3f},{v.y:.3f},{v.z:.3f})"
+
+    x, y, z = (round(math.degrees(xyz)) for xyz in v.to_euler()[:])
+    return f"Euler({x},{y},{z})"
+
+
+def assert_vector3_equals(
+    expected: Vector, actual: Sequence[float], message: str
+) -> None:
+    if len(actual) != 3:
+        message = f"actual length is not 3: {actual}"
+        raise AssertionError(message)
+
+    threshold = 0.0001
+    if abs(expected[0] - actual[0]) > threshold:
+        message = f"{message}: {tuple(expected)} is different from {tuple(actual)}"
+        raise AssertionError(message)
+    if abs(expected[1] - actual[1]) > threshold:
+        message = f"{message}: {tuple(expected)} is different from {tuple(actual)}"
+        raise AssertionError(message)
+    if abs(expected[2] - actual[2]) > threshold:
+        message = f"{message}: {tuple(expected)} is different from {tuple(actual)}"
+        raise AssertionError(message)
+
+
+def cleanse_modules() -> None:
+    """Search for your plugin modules in blender python sys.modules and remove them.
+
+    To support reload properly, try to access a package var, if it's there,
+    reload everything.
+
+    This function may cause errors that are difficult to investigate. Please use with
+    caution. See also:
+    https://github.com/saturday06/VRM-Addon-for-Blender/issues/506#issuecomment-2183766778
+    """
+    import sys
+
+    all_modules = sys.modules
+    all_modules = dict(sorted(all_modules.items(), key=lambda x: x[0]))  # sort them
+
+    for k in all_modules:
+        if k == __name__ or k.startswith(__name__ + "."):
+            del sys.modules[k]