feat(errors): add centralized exception handling

src/stores/auth/auth-machine.ts

@@ -3,6 +3,7 @@
  */
 import { setup, assign } from "xstate";
 
+import { ExceptionHandler } from "@/core/errors";
 import type { AuthProvider } from "@/lib/auth/auth_platform";
 
 import { AuthState, initialState } from "./auth-state";
@@ -23,6 +24,9 @@ export type { AuthState } from "./auth-state";
 export { initialState } from "./auth-state";
 export type { AuthEvent } from "./auth-events";
 
+const toAuthErrorMessage = (error: unknown): string =>
+  ExceptionHandler.message(error);
+
 // ============================================================
 // Machine
 //
@@ -119,8 +123,7 @@ export const authMachine = setup({
         onError: {
           target: "idle",
           actions: assign({
-            errorMessage: ({ event }) =>
-              event.error instanceof Error ? event.error.message : String(event.error),
+            errorMessage: ({ event }) => toAuthErrorMessage(event.error),
             hasInitialized: true,
           }),
         },
@@ -145,8 +148,7 @@ export const authMachine = setup({
         onError: {
           target: "idle",
           actions: assign({
-            errorMessage: ({ event }) =>
-              event.error instanceof Error ? event.error.message : String(event.error),
+            errorMessage: ({ event }) => toAuthErrorMessage(event.error),
             hasInitialized: true,
           }),
         },
@@ -174,8 +176,7 @@ export const authMachine = setup({
         onError: {
           target: "idle",
           actions: assign({
-            errorMessage: ({ event }) =>
-              event.error instanceof Error ? event.error.message : String(event.error),
+            errorMessage: ({ event }) => toAuthErrorMessage(event.error),
             hasInitialized: true,
           }),
         },
@@ -208,8 +209,7 @@ export const authMachine = setup({
         onError: {
           target: "idle",
           actions: assign({
-            errorMessage: ({ event }) =>
-              event.error instanceof Error ? event.error.message : String(event.error),
+            errorMessage: ({ event }) => toAuthErrorMessage(event.error),
             hasInitialized: true,
           }),
         },
@@ -231,8 +231,7 @@ export const authMachine = setup({
         onError: {
           target: "idle",
           actions: assign({
-            errorMessage: ({ event }) =>
-              event.error instanceof Error ? event.error.message : String(event.error),
+            errorMessage: ({ event }) => toAuthErrorMessage(event.error),
           }),
         },
       },
@@ -254,8 +253,7 @@ export const authMachine = setup({
           actions: assign(({ event }) => ({
             ...initialState,
             hasInitialized: true,
-            errorMessage:
-              event.error instanceof Error ? event.error.message : String(event.error),
+            errorMessage: toAuthErrorMessage(event.error),
           })),
         },
       },
@@ -281,8 +279,7 @@ export const authMachine = setup({
         onError: {
           target: "idle",
           actions: assign({
-            errorMessage: ({ event }) =>
-              event.error instanceof Error ? event.error.message : String(event.error),
+            errorMessage: ({ event }) => toAuthErrorMessage(event.error),
             hasInitialized: true,
           }),
         },
@@ -309,8 +306,7 @@ export const authMachine = setup({
         onError: {
           target: "idle",
           actions: assign({
-            errorMessage: ({ event }) =>
-              event.error instanceof Error ? event.error.message : String(event.error),
+            errorMessage: ({ event }) => toAuthErrorMessage(event.error),
             hasInitialized: true,
           }),
         },

src/stores/chat/chat-send-flow.ts

@@ -1,5 +1,6 @@
 import { fromCallback, fromPromise } from "xstate";
 
+import { ExceptionHandler } from "@/core/errors";
 import { MessageQueue } from "@/core/net/message-queue";
 import type { ChatSendResponse } from "@/data/dto/chat";
 import { getChatRepository } from "@/data/repositories/chat_repository";
@@ -131,8 +132,7 @@ function createMessageQueueActor(
       const output = await sendMessageViaHttp(content);
       sendBack({ type: "ChatQueuedHttpDone", output });
     } catch (error) {
-      const errorMessage =
-        error instanceof Error ? error.message : "Message send failed";
+      const errorMessage = ExceptionHandler.message(error);
       log.error("[chat-machine] message queue send failed", {
         error,
       });

src/stores/payment/payment-machine.helpers.ts

@@ -1,3 +1,4 @@
+import { ExceptionHandler } from "@/core/errors";
 import { PaymentPlan, type PaymentPlansResponse } from "@/data/dto/payment";
 
 import type { PaymentState } from "./payment-state";
@@ -7,7 +8,7 @@ export const PAYMENT_TIMEOUT_ERROR_MESSAGE =
   "Payment timed out. Please try again.";
 
 export function toPaymentErrorMessage(error: unknown): string {
-  return error instanceof Error ? error.message : String(error);
+  return ExceptionHandler.message(error);
 }
 
 export function hasOrderPollingTimedOut(