feat: enhance AppConfig loading to merge default providers and set API key

src/controller/input.rs

@@ -280,6 +280,12 @@ fn handle_overlay_enter(state: &mut AppStateRest) -> Vec<Action> {
                     let model = cfg.default_model.clone().unwrap_or_else(|| "claude-opus-4-8".to_string());
                     state.settings.provider = provider.clone();
                     state.settings.model = model.clone();
+                    // Set API key from provider's default if not already configured
+                    if state.settings.api_key.is_none() || state.settings.api_key.as_deref() == Some("") {
+                        if let Some(ref key) = cfg.default_api_key {
+                            state.settings.api_key = Some(key.clone());
+                        }
+                    }
                     let _ = state.settings.save();
                     state.push_toast(crate::app::state::types::Toast::new(
                         crate::app::state::types::ToastKind::Success,

src/model/app_config.rs

@@ -60,9 +60,15 @@ impl AppConfig {
     pub fn load() -> Self {
         let store = super::store::Store::new();
         let path = store.base_dir.join("app_config.json");
-        std::fs::read_to_string(path)
+        let mut cfg: AppConfig = std::fs::read_to_string(path)
             .ok()
             .and_then(|s| serde_json::from_str(&s).ok())
-            .unwrap_or_default()
+            .unwrap_or_default();
+        // Merge any default providers not present in the loaded config
+        let defaults = Self::default();
+        for (name, provider) in defaults.providers {
+            cfg.providers.entry(name).or_insert(provider);
+        }
+        cfg
     }
 }