fix: surface errors and polish UX across Step Library and Batch pages (#92)

- StepLibraryPage: replace silent console.error with toast.error on edit/save
  failures; replace manual setTimeout toast with toast.success helper
- BatchStatusPage: add error state with retry button for failed session loads
  instead of showing ambiguous "No sessions found"
- StepDetailModal: guard clipboard copy against browser denial (no false
  "Copied!" state on permission error); fix dead "See all reviews" button
  with inline expand/collapse toggle
- StepLibraryBrowser: add "Try again" retry button to error state; retry
  increments a counter that re-triggers both load effects

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

frontend/src/pages/BatchStatusPage.tsx

@@ -21,6 +21,7 @@ export default function BatchStatusPage() {
   const [sessions, setSessions] = useState<Session[]>([])
   const [isLoading, setIsLoading] = useState(true)
   const [isRefreshing, setIsRefreshing] = useState(false)
+  const [loadError, setLoadError] = useState<string | null>(null)
   const [batchDate, setBatchDate] = useState<Date | null>(null)
   const pollRef = useRef<ReturnType<typeof setInterval> | null>(null)
 
@@ -30,9 +31,12 @@ export default function BatchStatusPage() {
     try {
       const data = await sessionsApi.list({ batch_id: batchId, size: 100 })
       setSessions(Array.isArray(data) ? data : [])
+      setLoadError(null)
       if (data.length > 0 && data[0].started_at) {
         setBatchDate(new Date(data[0].started_at))
       }
+    } catch {
+      setLoadError('Failed to load batch sessions')
     } finally {
       if (showRefreshing) setIsRefreshing(false)
     }
@@ -48,6 +52,8 @@ export default function BatchStatusPage() {
           loadSessions(),
         ])
         setTree(treeData)
+      } catch {
+        setLoadError('Failed to load batch data')
       } finally {
         setIsLoading(false)
       }
@@ -178,7 +184,17 @@ export default function BatchStatusPage() {
 
       {/* Target cards */}
       <div className="space-y-2">
-        {sessions.length === 0 ? (
+        {loadError ? (
+          <div className="rounded-lg border border-red-400/20 bg-red-400/10 p-4 text-center">
+            <p className="text-sm text-red-400 mb-3">{loadError}</p>
+            <button
+              onClick={() => loadSessions(true)}
+              className="rounded-md border border-border px-3 py-1.5 text-sm text-muted-foreground hover:bg-accent hover:text-foreground transition-colors"
+            >
+              Try again
+            </button>
+          </div>
+        ) : sessions.length === 0 ? (
           <p className="text-center text-[0.875rem] text-muted-foreground py-8">
             No sessions found for this batch.
           </p>
@@ -207,3 +223,4 @@ export default function BatchStatusPage() {
     </div>
   )
 }
+