feat(tui): workflow-start intent input box wired to StartSession.input

apps/tui-go/internal/protocol/protocol.go

@@ -213,9 +213,14 @@ func ChatInput(sessionID, text, mode string) []byte {
 	return encode("ChatInput", map[string]any{"sessionId": sessionID, "text": text, "mode": mode})
 }
 
-// StartSession launches a workflow-backed session.
-func StartSession(workflowID string) []byte {
-	return encode("StartSession", map[string]any{"workflowId": workflowID, "config": nil})
+// StartSession launches a workflow-backed session. input is the optional freeform request
+// seeded into the decision journal; pass "" for fixed-task workflows (e.g. healthcheck).
+func StartSession(workflowID, input string) []byte {
+	msg := map[string]any{"workflowId": workflowID, "config": nil}
+	if input != "" {
+		msg["input"] = input
+	}
+	return encode("StartSession", msg)
 }
 
 // CancelSession cancels a running session.