feat(provider): expose Atomic Chat in /provider picker with autodetect (#810)

Adds Atomic Chat as a first-class preset inside the in-session /provider
slash command, mirroring the Ollama auto-detect flow. Picking it probes
127.0.0.1:1337/v1/models, lists loaded models for direct selection, and
falls back to "Enter manually" / "Back" when the server is unreachable
or no models are loaded. README updated to reflect the new setup path.

Made-with: Cursor

src/utils/providerProfiles.ts

@@ -33,6 +33,7 @@ export type ProviderPreset =
   | 'custom'
   | 'nvidia-nim'
   | 'minimax'
+  | 'atomic-chat'
 
 export type ProviderProfileInput = {
   provider?: ProviderProfile['provider']
@@ -285,6 +286,15 @@ export function getProviderPresetDefaults(
         apiKey: process.env.MINIMAX_API_KEY ?? '',
         requiresApiKey: true,
       }
+    case 'atomic-chat':
+      return {
+        provider: 'openai',
+        name: 'Atomic Chat',
+        baseUrl: 'http://127.0.0.1:1337/v1',
+        model: process.env.OPENAI_MODEL ?? 'local-model',
+        apiKey: '',
+        requiresApiKey: false,
+      }
     case 'ollama':
     default:
       return {