Derive picture frame size from picture texture aspect ratio

Replace Width/Height with a single Size (longer side); the shorter side
follows the picture material's base map source-image aspect (editor-
resolved, serialized for builds, 1:1 fallback). Add Range attributes on
all frame parameters and default material references (new Frame.mat).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Assets/Scripts/Components/PictureFrameBuilder.cs.meta

@@ -1,2 +1,15 @@
 fileFormatVersion: 2
-guid: 86a75d0253697424fb4b506c394f13bc
+guid: 86a75d0253697424fb4b506c394f13bc
+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences:
+  - _pictureMaterial: {instanceID: 0}
+  - _innerMaterial: {fileID: 2100000, guid: a7794896ef878a64399cca929db5c43c, type: 2}
+  - _frameMaterial: {fileID: 2100000, guid: a7794896ef878a64399cca929db5c43c, type: 2}
+  - _backMaterial: {fileID: 2100000, guid: a7794896ef878a64399cca929db5c43c, type: 2}
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: