docs: refresh README product hero

[spytensor]

What changed

• Replaced the English and Simplified Chinese README hero images.
• Updated the product montage to show the current workspace, active execution state, Run details, and parallel Plan graph.
• Preserved the restrained MOZI visual system and localized the two hero variants.

Why

The previous hero used older product surfaces and did not show MOZI's transparent execution and parallel planning experience.

Validation

• Confirmed both PNGs are 1672 × 941 RGB images.
• Confirmed README.md and README.zh-CN.md still reference the expected asset paths.
• Ran git diff --check.
• Ran pnpm verify:public-export successfully.
• Visually inspected both final images at original resolution.

No product code or runtime behavior changed.