feat: comment-triggered wakeups, coalescing improvements, and failed run badges

Enhance heartbeat wakeup to propagate wakeCommentId, queue follow-up runs
for comment wakes on already-running agents, and merge coalesced context
snapshots. Add failed run count to sidebar badges and expose usage/result
JSON in activity service.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/services/activity.ts

@@ -70,6 +70,8 @@ export function activityService(db: Db) {
           finishedAt: heartbeatRuns.finishedAt,
           createdAt: heartbeatRuns.createdAt,
           invocationSource: heartbeatRuns.invocationSource,
+          usageJson: heartbeatRuns.usageJson,
+          resultJson: heartbeatRuns.resultJson,
         })
         .from(activityLog)
         .innerJoin(heartbeatRuns, eq(activityLog.runId, heartbeatRuns.id))