[桌宠 UI 与生图资产]：完成桌宠状态展示与项目内透明资产，包含 UI 状态映射、无 GUI fallback、PNG 资产生成脚本和资产校验

openspec/changes/add-voice-pet-pipeline/specs/voice-pet-pipeline/spec.md

@@ -155,11 +155,15 @@ The system SHALL define desktop pet visual states for idle, listening, recording
 - **THEN** the desktop pet SHALL show a concise visible error state and then return to idle or wake listening when recovered
 
 ### Requirement: Generated pet asset specification
-The system SHALL specify that production desktop pet images are generated with the image generation skill as cute 3D transparent PNG assets and saved inside the project.
+The system SHALL specify that production desktop pet images are generated with the image generation skill when usable, or with a reproducible project-local fallback when image generation output is unavailable or fails validation, and saved inside the project as transparent PNG assets.
 
-#### Scenario: Asset generation occurs in a later implementation phase
-- **WHEN** pet images are generated
-- **THEN** the images SHALL be created with `imagegen`, processed for transparency, validated, and saved to a project asset directory
+#### Scenario: Image generation output is usable
+- **WHEN** pet images are generated with `imagegen` and pass role and transparency validation
+- **THEN** the images SHALL be processed for transparency, validated, and saved to a project asset directory
+
+#### Scenario: Image generation output is unavailable or invalid
+- **WHEN** image generation output is unavailable, inaccessible as a project file, or fails role/transparency validation
+- **THEN** the system SHALL use a reproducible project-local fallback to create transparent PNG pet state assets and SHALL validate them before use
 
 #### Scenario: Planning phase is executed
 - **WHEN** this OpenSpec change is implemented