fix: Refine flow — optimistic UI update + instruction passthrough

- Add getActiveRefineAgent to spawn mutation optimistic updates and
  live event invalidation rules so the refine panel reflects agent
  state immediately without manual refresh
- Accept optional instruction param in buildRefinePrompt() and inject
  it as <user_instruction> block so the agent knows what to focus on
- Pass input.instruction through in architect router spawn call

apps/web/src/hooks/useRefineAgent.ts

@@ -110,9 +110,11 @@ export function useRefineAgent(initiativeId: string): UseRefineAgentResult {
     onMutate: async ({ initiativeId, instruction }) => {
       // Cancel outgoing refetches
       await utils.listAgents.cancel();
+      await utils.getActiveRefineAgent.cancel({ initiativeId });
 
-      // Snapshot previous value
+      // Snapshot previous values
       const previousAgents = utils.listAgents.getData();
+      const previousRefineAgent = utils.getActiveRefineAgent.getData({ initiativeId });
 
       // Optimistically add a temporary agent
       const tempAgent = {
@@ -133,20 +135,25 @@ export function useRefineAgent(initiativeId: string): UseRefineAgentResult {
       };
 
       utils.listAgents.setData(undefined, (old = []) => [tempAgent, ...old]);
+      utils.getActiveRefineAgent.setData({ initiativeId }, tempAgent as any);
 
-      return { previousAgents };
+      return { previousAgents, previousRefineAgent };
     },
     onSuccess: () => {
       // Agent will appear in the list after invalidation
     },
     onError: (err, variables, context) => {
-      // Revert optimistic update
+      // Revert optimistic updates
       if (context?.previousAgents) {
         utils.listAgents.setData(undefined, context.previousAgents);
       }
+      if (context?.previousRefineAgent !== undefined) {
+        utils.getActiveRefineAgent.setData({ initiativeId }, context.previousRefineAgent);
+      }
     },
     onSettled: () => {
       void utils.listAgents.invalidate();
+      void utils.getActiveRefineAgent.invalidate({ initiativeId });
     },
   });
 

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

@@ -31,7 +31,7 @@ function InitiativeDetailPage() {
   useLiveUpdates([
     { prefix: 'task:',  invalidate: ['listPhases', 'listTasks', 'listInitiativeTasks'] },
     { prefix: 'phase:', invalidate: ['listPhases', 'listTasks', 'listInitiativePhaseDependencies'] },
-    { prefix: 'agent:', invalidate: ['listAgents'] },
+    { prefix: 'agent:', invalidate: ['listAgents', 'getActiveRefineAgent'] },
     { prefix: 'page:',  invalidate: ['listPages', 'getPage', 'getRootPage'] },
   ]);