fix: display tauri error messages instead of object dumps

src/components/projects/ProjectForm.tsx

@@ -2,6 +2,7 @@ import { useState, useEffect } from "react";
 import { useNavigate, useParams } from "react-router-dom";
 import { open } from "@tauri-apps/plugin-dialog";
 import { createProject, getProject, updateProject } from "../../lib/api";
+import { getErrorMessage } from "../../lib/errors";
 
 export default function ProjectForm() {
   const navigate = useNavigate();
@@ -49,8 +50,7 @@ export default function ProjectForm() {
       window.dispatchEvent(new Event("orchai:refresh-projects"));
       navigate("/");
     } catch (err: unknown) {
-      const message = err instanceof Error ? err.message : String(err);
-      setError(message);
+      setError(getErrorMessage(err));
     } finally {
       setLoading(false);
     }

src/components/settings/SettingsPage.tsx

@@ -5,6 +5,7 @@ import {
   deleteTuleapCredentials,
   testTuleapConnection,
 } from "../../lib/api";
+import { getErrorMessage } from "../../lib/errors";
 import type { TuleapCredentialsSafe } from "../../lib/types";
 
 export default function SettingsPage() {
@@ -43,7 +44,7 @@ export default function SettingsPage() {
       setPassword("");
       setSuccess("Credentials saved.");
     } catch (err: unknown) {
-      setError(err instanceof Error ? err.message : String(err));
+      setError(getErrorMessage(err));
     } finally {
       setSaving(false);
     }
@@ -56,7 +57,7 @@ export default function SettingsPage() {
       const msg = await testTuleapConnection();
       setSuccess(msg);
     } catch (err: unknown) {
-      setError(err instanceof Error ? err.message : String(err));
+      setError(getErrorMessage(err));
     } finally {
       setTesting(false);
     }
@@ -74,7 +75,7 @@ export default function SettingsPage() {
       setPassword("");
       setSuccess("Credentials deleted.");
     } catch (err: unknown) {
-      setError(err instanceof Error ? err.message : String(err));
+      setError(getErrorMessage(err));
     } finally {
       setDeleting(false);
     }

src/components/tickets/TicketDetail.tsx

@@ -10,6 +10,7 @@ import {
   getWorktreeDiff,
   retryTicket,
 } from "../../lib/api";
+import { getErrorMessage } from "../../lib/errors";
 import type { ProcessedTicket, Worktree } from "../../lib/types";
 
 function statusBadgeClass(status: string): string {
@@ -88,7 +89,7 @@ export default function TicketDetail() {
         setDiff(null);
       }
     } catch (err) {
-      setError(err instanceof Error ? err.message : String(err));
+      setError(getErrorMessage(err));
     }
   }
 
@@ -103,7 +104,7 @@ export default function TicketDetail() {
       await retryTicket(ticketId);
       await loadData();
     } catch (err) {
-      setError(err instanceof Error ? err.message : String(err));
+      setError(getErrorMessage(err));
     }
     setLoading(false);
   }
@@ -115,7 +116,7 @@ export default function TicketDetail() {
       await cancelTicket(ticketId);
       await loadData();
     } catch (err) {
-      setError(err instanceof Error ? err.message : String(err));
+      setError(getErrorMessage(err));
     }
     setLoading(false);
   }
@@ -128,7 +129,7 @@ export default function TicketDetail() {
       await applyFixToBranch(worktree.id, targetBranch);
       await loadData();
     } catch (err) {
-      setError(err instanceof Error ? err.message : String(err));
+      setError(getErrorMessage(err));
     }
     setLoading(false);
   }
@@ -142,7 +143,7 @@ export default function TicketDetail() {
       setWorktree(null);
       setDiff(null);
     } catch (err) {
-      setError(err instanceof Error ? err.message : String(err));
+      setError(getErrorMessage(err));
     }
     setLoading(false);
   }

src/components/trackers/TrackerConfig.tsx

@@ -1,6 +1,7 @@
 import { useState } from "react";
 import { useParams, useNavigate } from "react-router-dom";
 import { addTracker, getTrackerFields } from "../../lib/api";
+import { getErrorMessage } from "../../lib/errors";
 import type { FilterGroup, TrackerField, AgentConfig } from "../../lib/types";
 import FilterBuilder from "./FilterBuilder";
 
@@ -29,7 +30,7 @@ export default function TrackerConfig() {
       setFields(result);
       setFieldsLoaded(true);
     } catch (err: unknown) {
-      setError(err instanceof Error ? err.message : String(err));
+      setError(getErrorMessage(err));
     } finally {
       setFieldsLoading(false);
     }
@@ -52,7 +53,7 @@ export default function TrackerConfig() {
       await addTracker(projectId, Number(trackerId), trackerLabel, pollingInterval, agentConfig, filters);
       navigate(`/projects/${projectId}`);
     } catch (err: unknown) {
-      setError(err instanceof Error ? err.message : String(err));
+      setError(getErrorMessage(err));
     } finally {
       setLoading(false);
     }

src/lib/errors.ts

@@ -0,0 +1,40 @@
+export function getErrorMessage(err: unknown): string {
+  if (err instanceof Error) {
+    return err.message;
+  }
+
+  if (typeof err === "string") {
+    return err;
+  }
+
+  if (err && typeof err === "object") {
+    const withMessage = err as { message?: unknown; error?: unknown };
+
+    if (typeof withMessage.message === "string") {
+      return withMessage.message;
+    }
+
+    if (typeof withMessage.error === "string") {
+      return withMessage.error;
+    }
+
+    if (
+      withMessage.message &&
+      typeof withMessage.message === "object" &&
+      "message" in withMessage.message
+    ) {
+      const nested = withMessage.message as { message?: unknown };
+      if (typeof nested.message === "string") {
+        return nested.message;
+      }
+    }
+
+    try {
+      return JSON.stringify(err);
+    } catch {
+      // fallthrough to String below
+    }
+  }
+
+  return String(err);
+}