Add canonical per-provider model lists with picker UI

The catalog only carried one defaultModel string per provider, which
forced users to type model ids by hand and made the onboarding /
providers panel feel like the original AgentCompany was missing models.

- src/shared/provider-models.ts holds the canonical id/name list per
  provider key (~165 entries across OpenAI, Anthropic, xAI, Groq,
  GitHub Copilot, Antigravity, GPT account, Azure, Bedrock, Vertex)
- ProviderCatalogEntry now exposes a models[] array
- Onboarding ProviderStep renders a <select> populated from the active
  provider's catalog instead of a freeform text input
- ProvidersPanel connect dialog uses the same picker for API key,
  OAuth, and account auth flows
- TeamPage hire dialog adds a <datalist> with every catalog model so
  manual entry is autocompletable

AgentCompany-New/src/shared/domain.ts

@@ -273,6 +273,11 @@ export interface ProviderRecord {
   createdAt: string;
 }
 
+export interface ProviderCatalogModel {
+  id: string;
+  name: string;
+}
+
 export interface ProviderCatalogEntry {
   key: string;
   label: string;
@@ -281,6 +286,7 @@ export interface ProviderCatalogEntry {
   capabilityTags: string[];
   signInUrl: string | null;
   credentialHelp: string;
+  models: ProviderCatalogModel[];
 }
 
 export interface ProviderRequestRecord {