fix: route new prompt sync to target directory

Keeps optimistic prompt state in the session directory
Routes live assistant part updates using upstream event payloads
Adds regressions for startup session switch races

packages/ui/src/sync/session-ui-store.ts

@@ -111,6 +111,7 @@ export function routeMessage(params: {
         providerID: params.providerID,
         modelID: params.modelID,
         agent: params.agent,
+        directory: requestDirectory,
         files: params.files,
         send: (messageID) => opencodeClient.sendCommand({
           id: params.sessionId,
@@ -135,6 +136,7 @@ export function routeMessage(params: {
     providerID: params.providerID,
     modelID: params.modelID,
     agent: params.agent,
+    directory: requestDirectory,
     files: params.files,
     send: (messageID) => opencodeClient.sendMessage({
       id: params.sessionId,