* refactor(basic-host): use SDK types for ModelContext and AppMessage
- Import McpUiUpdateModelContextRequest and McpUiMessageRequest from SDK
- Replace custom ModelContext with McpUiUpdateModelContextRequest['params']
- Replace custom AppMessage with McpUiMessageRequest['params']
- Pass full message params instead of extracting text
- Format messages by extracting text from content blocks in display
* feat(basic-host): handle non-text content blocks in display
- Add formatContentBlock helper for text, image, audio, resource types
- Show placeholders like <image: image/png> for non-text content
- Apply to both messages and model context display
* test: update shadertoy screenshot
* test: update screenshots from CI (linux x64)
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