FEAT-3: fix unhandled ApiError rejections (catch in form submits + dev unhandledrejection guard, ApiError carries path)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

gerbil-manager-web/src/api/client.ts

@@ -10,11 +10,14 @@ export const API_BASE_URL: string =
 
 export class ApiError extends Error {
   readonly status: number | null
+  /** The request path that failed (for diagnostics/logging). */
+  readonly path?: string
 
-  constructor(message: string, status: number | null) {
+  constructor(message: string, status: number | null, path?: string) {
     super(message)
     this.name = 'ApiError'
     this.status = status
+    this.path = path
   }
 }
 
@@ -32,11 +35,11 @@ async function request<T>(path: string, init?: RequestInit): Promise<T> {
       ...init,
     })
   } catch {
-    throw new ApiError(de.api.errors.network, null)
+    throw new ApiError(de.api.errors.network, null, path)
   }
 
   if (!response.ok) {
-    throw new ApiError(errorMessageFor(response.status), response.status)
+    throw new ApiError(errorMessageFor(response.status), response.status, path)
   }
 
   if (response.status === 204) {

gerbil-manager-web/src/dev/unhandledRejectionGuard.ts

@@ -0,0 +1,25 @@
+import { ApiError } from '../api/client'
+
+/**
+ * Dev-only safety net for unhandled promise rejections.
+ *
+ * Call sites should still handle their own errors (useApi error UI, try/catch
+ * around mutations). This guard exists so that any STRAY rejection — typically
+ * an ApiError from an endpoint that hasn't shipped yet — is logged with its
+ * failing path instead of spamming the console with "Uncaught (in promise)".
+ * It surfaces regressions (which endpoint, which status) without turning the
+ * page into a dead end. No-op in production builds.
+ */
+export function installUnhandledRejectionGuard(): void {
+  if (!import.meta.env.DEV) return
+  window.addEventListener('unhandledrejection', (event) => {
+    const reason = event.reason
+    if (reason instanceof ApiError) {
+      const where = reason.path ? ` [${reason.path}]` : ''
+      console.warn(`[API] Unbehandelte Ablehnung${where} (${reason.status ?? 'Netzwerk'}): ${reason.message}`)
+      event.preventDefault()
+    } else {
+      console.warn('[Unbehandelte Promise-Ablehnung]', reason)
+    }
+  })
+}

gerbil-manager-web/src/main.tsx

@@ -2,6 +2,9 @@ import { StrictMode } from 'react'
 import { createRoot } from 'react-dom/client'
 import './index.css'
 import App from './App.tsx'
+import { installUnhandledRejectionGuard } from './dev/unhandledRejectionGuard'
+
+installUnhandledRejectionGuard()
 
 createRoot(document.getElementById('root')!).render(
   <StrictMode>

gerbil-manager-web/src/pages/GerbilFormPage.tsx

@@ -166,8 +166,13 @@ export default function GerbilFormPage() {
       genotype: nn(form.genotype),
       notes: nn(form.notes),
     }
-    const saved = await mutation.run(body)
-    navigate(`/rennmaeuse/${saved.id}`)
+    try {
+      const saved = await mutation.run(body)
+      navigate(`/rennmaeuse/${saved.id}`)
+    } catch {
+      // Error is surfaced via mutation.error; swallow so the rejected promise
+      // from this async submit handler doesn't become an unhandled rejection.
+    }
   }
 
   if (isEdit && existing.loading) return <p className="muted">{de.common.loading}</p>

gerbil-manager-web/src/pages/WurfFormPage.tsx

@@ -116,8 +116,13 @@ export default function WurfFormPage() {
       expectedGoHomeDate: nn(form.expectedGoHomeDate),
       notes: nn(form.notes),
     }
-    const saved = await mutation.run(body)
-    navigate(`/wuerfe/${saved.id}`)
+    try {
+      const saved = await mutation.run(body)
+      navigate(`/wuerfe/${saved.id}`)
+    } catch {
+      // Error surfaced via mutation.error; swallow to avoid an unhandled
+      // rejection escaping this async submit handler.
+    }
   }
 
   if (isEdit && existing.loading) return <p className="muted">{de.common.loading}</p>