fix: show error toast when adding non-git folder (#321)

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

src/renderer/src/store/slices/repos.ts

@@ -3,6 +3,8 @@ import { toast } from 'sonner'
 import type { AppState } from '../types'
 import type { Repo } from '../../../../shared/types'
 
+const ERROR_TOAST_DURATION = 60_000
+
 export type RepoSlice = {
   repos: Repo[]
   activeRepoId: string | null
@@ -58,6 +60,19 @@ export const createRepoSlice: StateCreator<AppState, [], [], RepoSlice> = (set,
       return repo
     } catch (err) {
       console.error('Failed to add repo:', err)
+      const message = err instanceof Error ? err.message : String(err)
+      const duration = ERROR_TOAST_DURATION
+      if (message.includes('Not a valid git repository')) {
+        toast.error('Not a git repository', {
+          description: 'Only git repositories can be added. Initialize one with git init first.',
+          duration
+        })
+      } else {
+        toast.error('Failed to add repo', {
+          description: message,
+          duration
+        })
+      }
       return null
     }
   },