[WIP] Fix sample image loading issue

[Copilot]

• Identify the issue: Assets struct only embeds from assets directory with icons/**/*.svg pattern
• Update assets.rs to include src/fixtures directory in the embedded resources
• Test the fix by building and running the story application
• Verify the images load correctly

Original prompt

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This section details on the original issue you should resolve

<issue_title>The sample image cannot be loaded</issue_title>
<issue_description>2025-10-23T08:19:17.654004Z ERROR gpui::asset_cache: Failed to load asset: asset error: Embedded resource not found: src/fixtures/color-wheel.svg</issue_description>

<agent_instructions>To fix this issue</agent_instructions>

Comments on the Issue (you are @copilot in this section)

Fixes #1418

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[huacnlee]

@copilot continue