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/version.py

@@ -0,0 +1,161 @@
+# SPDX-License-Identifier: MIT OR GPL-3.0-or-later
+import platform
+from dataclasses import dataclass
+from sys import float_info
+from typing import Optional
+
+import bpy
+from bpy.app.translations import pgettext
+
+from .blender_manifest import BlenderManifest
+from .logger import get_logger
+
+logger = get_logger(__name__)
+
+
+@dataclass
+class Cache:
+    use: bool
+    last_blender_restart_required: bool
+    last_blender_manifest_modification_time: float
+    initial_blender_manifest_content: bytes
+
+
+cache = Cache(
+    use=False,
+    last_blender_restart_required=False,
+    last_blender_manifest_modification_time=0.0,
+    initial_blender_manifest_content=BlenderManifest.default_blender_manifest_path().read_bytes(),
+)
+
+
+def clear_addon_version_cache() -> Optional[float]:
+    cache.use = False
+    return None
+
+
+def trigger_clear_addon_version_cache() -> None:
+    if tuple(bpy.app.version) >= (4, 2):
+        return
+    if bpy.app.timers.is_registered(clear_addon_version_cache):
+        return
+    bpy.app.timers.register(clear_addon_version_cache, first_interval=0.5)
+
+
+def min_unsupported_blender_major_minor_version() -> Optional[tuple[int, int]]:
+    blender_version_max = BlenderManifest.read().blender_version_max
+    if blender_version_max is None:
+        return None
+    return (blender_version_max[0], blender_version_max[1])
+
+
+def get_addon_version() -> tuple[int, int, int]:
+    return BlenderManifest.read().version
+
+
+def blender_restart_required() -> bool:
+    if tuple(bpy.app.version) >= (4, 2):
+        return False
+
+    if cache.use:
+        return cache.last_blender_restart_required
+
+    cache.use = True
+
+    if cache.last_blender_restart_required:
+        return True
+
+    blender_manifest_path = BlenderManifest.default_blender_manifest_path()
+    blender_manifest_modification_time = blender_manifest_path.stat().st_mtime
+    if (
+        abs(
+            cache.last_blender_manifest_modification_time
+            - blender_manifest_modification_time
+        )
+        < float_info.epsilon
+    ):
+        return False
+
+    cache.last_blender_manifest_modification_time = blender_manifest_modification_time
+
+    blender_manifest_content = blender_manifest_path.read_bytes()
+    if blender_manifest_content == cache.initial_blender_manifest_content:
+        return False
+
+    cache.last_blender_restart_required = True
+    return True
+
+
+def stable_release() -> bool:
+    if bpy.app.version_cycle == "release":
+        return True
+
+    # Microsoft Store distributes RC versions of 3.3.11 and 3.6.3 as
+    # release versions.
+    return platform.system() == "Windows" and bpy.app.version_cycle == "rc"
+
+
+def supported() -> bool:
+    v = min_unsupported_blender_major_minor_version()
+    if v is None:
+        return True
+    return bpy.app.version[:2] < v
+
+
+def preferences_warning_message() -> Optional[str]:
+    if blender_restart_required():
+        return pgettext(
+            "The VRM add-on has been updated."
+            + " Please restart Blender to apply the changes."
+        )
+    if not stable_release():
+        return pgettext(
+            "VRM add-on is not compatible with Blender {blender_version_cycle}."
+        ).format(blender_version_cycle=bpy.app.version_cycle.capitalize())
+    if not supported():
+        return pgettext(
+            "The installed VRM add-on is not compatible with Blender {blender_version}."
+            + " Please upgrade the add-on.",
+        ).format(blender_version=".".join(map(str, bpy.app.version[:2])))
+    return None
+
+
+def panel_warning_message() -> Optional[str]:
+    if blender_restart_required():
+        return pgettext(
+            "The VRM add-on has been\n"
+            + "updated. Please restart Blender\n"
+            + "to apply the changes."
+        )
+    if not stable_release():
+        return pgettext(
+            "VRM add-on is\n"
+            + "not compatible with\n"
+            + "Blender {blender_version_cycle}."
+        ).format(blender_version_cycle=bpy.app.version_cycle.capitalize())
+    if not supported():
+        return pgettext(
+            "The installed VRM add-\n"
+            + "on is not compatible with\n"
+            + "Blender {blender_version}. Please update."
+        ).format(blender_version=".".join(map(str, bpy.app.version[:2])))
+    return None
+
+
+def validation_warning_message() -> Optional[str]:
+    if blender_restart_required():
+        return pgettext(
+            "The VRM add-on has been updated."
+            + " Please restart Blender to apply the changes."
+        )
+    if not stable_release():
+        return pgettext(
+            "VRM add-on is not compatible with Blender {blender_version_cycle}."
+            + " The VRM may not be exported correctly.",
+        ).format(blender_version_cycle=bpy.app.version_cycle.capitalize())
+    if not supported():
+        return pgettext(
+            "The installed VRM add-on is not compatible with Blender {blender_version}."
+            + " The VRM may not be exported correctly."
+        ).format(blender_version=".".join(map(str, bpy.app.version)))
+    return None