Explain blocked schedule runs and let a failed document be processed again

Schedule history now shows a readable reason instead of the engine's raw code,
and under the newest run stopped by knowledge_not_ready it lists the Library
material that blocks it, with a link to fix it in Learning Studio. The list
refreshes while that material is still processing or building.

Upload gets a "Process again" button for a failed document, using the engine's
new reprocess endpoint; a knowledge base the document already has is kept. A
document being processed again no longer shows as "In the Brain".

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/express/schedules.ts

@@ -355,8 +355,22 @@ export interface RunSummary {
   trigger_kind: string
   safe_error_code: string | null
   budget_spent: number | null
+  has_readiness_issues: boolean
   created_at: string
   finished_at: string | null
 }
 
 export const listRuns = (id: number) => request<RunSummary[]>(`${AGENTS}/${id}/runs`)
+
+// What stops a run with knowledge_not_ready. The engine checks the whole Library, so a blocking
+// document need not be part of the schedule's chosen material. This is the current state, not the run's.
+export interface ReadinessIssue {
+  kind: 'document' | 'compose_set'
+  resource_id: number
+  title: string
+  reason: string
+  action_url: string
+}
+
+export const knowledgeReadiness = (id: number) =>
+  request<{ ready: boolean; issues: ReadinessIssue[] }>(`${AGENTS}/${id}/knowledge-readiness`)