fix: Replace getTaskAgent polling with event-driven invalidation

Add getTaskAgent to the agent: prefix SSE invalidation rule so spawned
agents are picked up immediately instead of polling every 5s.

apps/web/src/components/execution/TaskSlideOver.tsx

@@ -337,7 +337,7 @@ export function TaskSlideOver({ onOpenChat }: TaskSlideOverProps) {
 function AgentLogsTab({ taskId }: { taskId: string }) {
   const { data: agent, isLoading } = trpc.getTaskAgent.useQuery(
     { taskId },
-    { refetchOnWindowFocus: false, refetchInterval: (query) => query.state.data ? false : 5000 },
+    { refetchOnWindowFocus: false },
   );
 
   if (isLoading) {

apps/web/src/routes/initiatives/$id.tsx

@@ -34,7 +34,7 @@ function InitiativeDetailPage() {
     { prefix: 'initiative:', invalidate: ['getInitiative'] },
     { prefix: 'task:',      invalidate: ['listPhases', 'listTasks', 'listInitiativeTasks', 'getPhaseDependencies', 'listPhaseTaskDependencies'] },
     { prefix: 'phase:',     invalidate: ['listPhases', 'listTasks', 'listInitiativePhaseDependencies', 'getPhaseDependencies'] },
-    { prefix: 'agent:',     invalidate: ['listAgents', 'getActiveRefineAgent'] },
+    { prefix: 'agent:',     invalidate: ['listAgents', 'getActiveRefineAgent', 'getTaskAgent', 'getActiveConflictAgent'] },
     { prefix: 'page:',      invalidate: ['listPages', 'getPage', 'getRootPage'] },
     { prefix: 'changeset:', invalidate: ['getChangeSet', 'listChangeSets'] },
     { prefix: 'preview:',   invalidate: ['listPreviews', 'getPreviewStatus'] },