Interleave failed runs with issues and approvals in inbox

Failed runs are no longer shown in a separate section. They are now
mixed into the main work items feed sorted by timestamp, matching
how approvals are already interleaved with issues.

Replaced the large FailedRunCard with a compact FailedRunInboxRow
that matches the ApprovalInboxRow visual style.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

ui/src/lib/inbox.ts

@@ -23,6 +23,11 @@ export type InboxWorkItem =
       kind: "approval";
       timestamp: number;
       approval: Approval;
+    }
+  | {
+      kind: "failed_run";
+      timestamp: number;
+      run: HeartbeatRun;
     };
 
 export interface InboxBadgeData {
@@ -146,9 +151,11 @@ export function approvalActivityTimestamp(approval: Approval): number {
 export function getInboxWorkItems({
   issues,
   approvals,
+  failedRuns = [],
 }: {
   issues: Issue[];
   approvals: Approval[];
+  failedRuns?: HeartbeatRun[];
 }): InboxWorkItem[] {
   return [
     ...issues.map((issue) => ({
@@ -161,6 +168,11 @@ export function getInboxWorkItems({
       timestamp: approvalActivityTimestamp(approval),
       approval,
     })),
+    ...failedRuns.map((run) => ({
+      kind: "failed_run" as const,
+      timestamp: normalizeTimestamp(run.createdAt),
+      run,
+    })),
   ].sort((a, b) => {
     const timestampDiff = b.timestamp - a.timestamp;
     if (timestampDiff !== 0) return timestampDiff;