Model Advisor Block

Ranked on-device model recommendations that compute their OWN device context via useCapabilities and rank useModelRecommendations / getModelRegistry over the in-memory registry with ZERO network: a 21-task grouped selector, ranked model-recommendation-card results with a device-context line + result-count + empty states, two-model comparison via model-comparison-panel (max 2, third replaces the older), and a collapsible custom-model registration form (11 ModelRegistryEntry fields, per-field validation, in-memory notice, registerModel() + refresh). No model download. Split from ui/blocks/device-model-lab (model advisor section).