feat: handle StopFailure hook event for API error turns (#224)

Parses [StopFailure Hook] from stderr, emits claude:stop-failure, and
transitions the character to error state with a toast notification.

src/lib/stores/toasts.test.ts

@@ -187,6 +187,33 @@ describe("toastStore", () => {
     });
   });
 
+  describe("addError", () => {
+    it("adds an error toast with the warning icon", () => {
+      toastStore.addError("Something went wrong");
+      const toasts = get(toastStore);
+      expect(toasts).toHaveLength(1);
+      const toast = toasts[0];
+      expect(toast.kind).toBe("info");
+      if (toast.kind === "info") {
+        expect(toast.message).toBe("Something went wrong");
+        expect(toast.icon).toBe("⚠️");
+        expect(typeof toast.id).toBe("string");
+        expect(toast.id.length).toBeGreaterThan(0);
+      }
+    });
+
+    it("auto-dismisses after 6000ms", () => {
+      toastStore.addError("Rate limit reached");
+      expect(get(toastStore)).toHaveLength(1);
+
+      vi.advanceTimersByTime(5999);
+      expect(get(toastStore)).toHaveLength(1);
+
+      vi.advanceTimersByTime(1);
+      expect(get(toastStore)).toHaveLength(0);
+    });
+  });
+
   describe("addUpdate", () => {
     it("adds a persistent update toast with the correct fields", () => {
       toastStore.addUpdate("2.0.0", "1.9.0", "https://example.com/release");

src/lib/stores/toasts.ts

@@ -68,6 +68,13 @@ function createToastStore() {
     setTimeout(() => remove(id), 4000);
   }
 
+  function addError(message: string) {
+    const id = crypto.randomUUID();
+    const toast: InfoToast = { id, kind: "info", message, icon: "⚠️" };
+    update((toasts) => [...toasts, toast]);
+    setTimeout(() => remove(id), 6000);
+  }
+
   function addAchievement(achievement: AchievementUnlockedEvent["achievement"]) {
     const id = crypto.randomUUID();
     const toast: AchievementToast = { id, kind: "achievement", achievement };
@@ -82,7 +89,7 @@ function createToastStore() {
     // Update toasts are persistent — no auto-dismiss
   }
 
-  return { subscribe, addInfo, addAchievement, addUpdate, remove };
+  return { subscribe, addInfo, addError, addAchievement, addUpdate, remove };
 }
 
 export const toastStore = createToastStore();

src/lib/tauri.ts

@@ -10,6 +10,7 @@ import type {
   ConnectionStatus,
   ElicitationEvent,
   PermissionPromptEvent,
+  StopFailureEvent,
   UserQuestionEvent,
 } from "$lib/types/messages";
 import type { CharacterState } from "$lib/types/states";
@@ -640,6 +641,24 @@ export async function initializeTauriListeners() {
     }
   );
   unlisteners.push(elicitationResultUnlisten);
+
+  const stopFailureUnlisten = await listen<StopFailureEvent>("claude:stop-failure", (event) => {
+    const { stop_reason, error_type } = event.payload;
+
+    characterState.setTemporaryState("error", 3000);
+
+    let message: string;
+    if (stop_reason === "rate_limit") {
+      message = "Rate limit reached";
+    } else if (stop_reason === "auth_failure" || stop_reason === "authentication") {
+      message = "Authentication failed";
+    } else {
+      message = `API error: ${stop_reason ?? error_type ?? "unknown"}`;
+    }
+
+    toastStore.addError(message);
+  });
+  unlisteners.push(stopFailureUnlisten);
 }
 
 export function cleanupTauriListeners() {

src/lib/types/messages.ts

@@ -176,6 +176,12 @@ export interface ElicitationResultEvent {
   conversation_id?: string;
 }
 
+export interface StopFailureEvent {
+  stop_reason?: string;
+  error_type?: string;
+  conversation_id?: string;
+}
+
 export type ConnectionStatus = "disconnected" | "connecting" | "connected" | "error";
 
 export interface Attachment {