When multiple providers share the same model name, the selector now
uses both model ID and provider as the unique identifier instead of
model name alone. Backend returns default_provider alongside default
model, and model switching sends provider to the config.
Fixes#52
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
NSelect dropdown is unusable with providers that have hundreds of models.
Replaced with a modal dialog featuring search filter, collapsible provider
groups, and click-to-select.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>