Redesign repository overview

[0xprogrammable]

What changed

• rebuild the repository cover animation with independently anchored plant movement and a static background
• add a reduced-motion fallback for the cover
• restructure the README around launch flow, model status, release evidence, Ethereum contracts, the builder program and security
• add dedicated Classic, Deep and builder ecosystem artwork using existing Programmable brand assets

Why

The previous cover moved like one elastic layer and the README did not communicate the product, model status or public evidence clearly enough.

Verification

• cover: 1774 × 887, 20 frames, 3.6-second loop, 4.72 MB
• logo and upper background remain pixel-identical across frames
• all relative README links resolve
• staged secret scan passed
• forge fmt --check
• forge build --sizes
• FOUNDRY_PROFILE=ci forge test (53 passed)

No contract source, model status or deployment evidence changed.