Match plugins.jsx, where every card cover gets a different pastel→bold gradient (Pink+Blue, Mint+Violet, Cream+Coral, etc). Previously every card painted the same Pink→Blue ramp, making the marketplace grid feel uniform. `plugin_cover_gradient(name)` hashes the plugin name into the design's 8-stop palette so the same plugin always lands on the same ramp without needing any new manifest fields. cargo test --workspace: 440 passed, 0 failed.