feat(errors): per-account error modal with persisted error list

Accounts finishing done_with_errors showed only a count and a single
last_error. This adds a modal listing every concrete error of the
account's most recent run.

- migration 0005: account_errors table (kind folder|message|account,
  folder, message_ref, error, created_at; ON DELETE CASCADE; indexed)
- store: AddAccountError / ClearAccountErrors / ListAccountErrors
- copy: OnError callback captures per-message error text (previously
  only counted), with a "UID N: subject" reference
- orchestrator: clear errors at run start; persist folder/message/
  account errors; cap 500 rows/account/run with a suppressed-note row
- api: GET /api/tasks/{id}/accounts/{accountId}/errors
- web: AccountErrorsModal, clickable ERRORS count, api + styles

Verified: migration applies on Postgres 18; store add/list/clear and
cascade tests pass against real pg; backend build/vet/test green; web
tsc+vite build and oxlint clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01U9Eq4JtWjyNTv5qat3B3mM

web/src/api.ts

@@ -157,6 +157,20 @@ export const setTaskSchedule = (taskId: number, intervalSeconds: number) =>
 
 export const listRuns = (taskId: number) => api<Run[]>(`/api/tasks/${taskId}/runs`)
 
+export interface AccountError {
+  id: number
+  account_id: number
+  run_id: number
+  kind: string // folder | message | account
+  folder: string
+  message_ref: string
+  error: string
+  created_at: string
+}
+
+export const listAccountErrors = (taskId: number, accountId: number) =>
+  api<AccountError[]>(`/api/tasks/${taskId}/accounts/${accountId}/errors`)
+
 export const importCSV = (id: number, file: File) => {
   const fd = new FormData()
   fd.append('file', file)

web/src/app.css

@@ -300,6 +300,16 @@
   white-space: nowrap;
 }
 
+/* error text inside the per-account errors modal: wrap long messages */
+.err-cell {
+  max-width: 420px;
+  white-space: normal;
+  word-break: break-word;
+  color: var(--fail);
+  font-size: 12px;
+  line-height: 1.4;
+}
+
 /* clear-log button: mirrors the .panel-label tab on the right edge */
 .log-clear {
   position: absolute;

web/src/components/AccountErrorsModal.tsx

@@ -0,0 +1,65 @@
+import { useEffect, useState } from 'react'
+import { Modal } from './Modal'
+import { listAccountErrors, type AccountError } from '../api'
+
+const fmt = (iso: string) => (iso ? new Date(iso).toLocaleString() : '—')
+
+export function AccountErrorsModal({
+  taskId,
+  account,
+  onClose,
+}: {
+  taskId: number
+  account: { id: number; src_login: string } | null
+  onClose: () => void
+}) {
+  const [errors, setErrors] = useState<AccountError[] | null>(null)
+  const [failed, setFailed] = useState(false)
+  const open = account !== null
+
+  useEffect(() => {
+    if (!account) return
+    setErrors(null)
+    setFailed(false)
+    listAccountErrors(taskId, account.id)
+      .then((e) => setErrors(e ?? []))
+      .catch(() => setFailed(true))
+  }, [taskId, account])
+
+  return (
+    <Modal open={open} title={account ? `Errors — ${account.src_login}` : 'Errors'} onClose={onClose} size="lg">
+      <div className="tbl-wrap">
+        <table className="tbl">
+          <thead>
+            <tr>
+              <th>Time</th>
+              <th>Kind</th>
+              <th>Folder</th>
+              <th>Message</th>
+              <th>Error</th>
+            </tr>
+          </thead>
+          <tbody>
+            {failed ? (
+              <tr className="empty-row"><td colSpan={5}>failed to load errors</td></tr>
+            ) : errors === null ? (
+              <tr className="empty-row"><td colSpan={5}>loading…</td></tr>
+            ) : errors.length === 0 ? (
+              <tr className="empty-row"><td colSpan={5}>no errors recorded</td></tr>
+            ) : (
+              errors.map((e) => (
+                <tr key={e.id}>
+                  <td>{fmt(e.created_at)}</td>
+                  <td>{e.kind}</td>
+                  <td>{e.folder || '—'}</td>
+                  <td>{e.message_ref || '—'}</td>
+                  <td className="err-cell">{e.error}</td>
+                </tr>
+              ))
+            )}
+          </tbody>
+        </table>
+      </div>
+    </Modal>
+  )
+}

web/src/pages/TaskDetail.tsx

@@ -5,6 +5,7 @@ import { StatusBadge } from '../components/StatusBadge'
 import { useConfirm } from '../components/ConfirmProvider'
 import { FolderMappingModal } from '../components/FolderMappingModal'
 import { RunLogModal } from '../components/RunLogModal'
+import { AccountErrorsModal } from '../components/AccountErrorsModal'
 
 const emptyAccount = { src_login: '', src_pass: '', dst_login: '', dst_pass: '' }
 
@@ -87,6 +88,7 @@ export function TaskDetail({ id }: { id: number }) {
   const [error, setError] = useState<string | null>(null)
   const [live, setLive] = useState<Record<number, LiveProgress>>({})
   const [showRuns, setShowRuns] = useState(false)
+  const [errorsFor, setErrorsFor] = useState<{ id: number; src_login: string } | null>(null)
   const fileInputRef = useRef<HTMLInputElement>(null)
 
   function reload() {
@@ -609,7 +611,19 @@ export function TaskDetail({ id }: { id: number }) {
                     </td>
                     <td className="num-cell">{live[a.id]?.copied ?? a.copied}</td>
                     <td className="num-cell">{live[a.id]?.skipped ?? a.skipped}</td>
-                    <td className="num-cell">{a.errors}</td>
+                    <td className="num-cell">
+                      {a.errors > 0 ? (
+                        <button
+                          type="button"
+                          className="link-btn danger"
+                          onClick={() => setErrorsFor({ id: a.id, src_login: a.src_login })}
+                        >
+                          {a.errors}
+                        </button>
+                      ) : (
+                        a.errors
+                      )}
+                    </td>
                     <td className="num-cell">
                       <div className="row-actions">
                         {a.status !== 'running' && data?.task.status !== 'running' && (
@@ -671,6 +685,7 @@ export function TaskDetail({ id }: { id: number }) {
         />
       )}
       <RunLogModal taskId={id} open={showRuns} onClose={() => setShowRuns(false)} />
+      <AccountErrorsModal taskId={id} account={errorsFor} onClose={() => setErrorsFor(null)} />
     </>
   )
 }