Add disabled state to Send/Queue buttons for visual feedback

EnhancedInput now exposes canSubmit state via onCanSubmitChange callback,
allowing parent components to show proper disabled styling when input is
empty or only has a locked agent without content. This fixes the issue
where buttons remained visually enabled even when clicking would have no
effect.

dashboard/src/app/control/control-client.tsx

@@ -1785,6 +1785,7 @@ export default function ControlClient() {
   const itemsRef = useRef<ChatItem[]>([]);
   const [draftInput, setDraftInput] = useLocalStorage("control-draft", "");
   const [input, setInput] = useState(draftInput);
+  const [canSubmitInput, setCanSubmitInput] = useState(false);
   const [lastMissionId, setLastMissionId] = useLocalStorage<string | null>(
     "control-last-mission-id",
     null
@@ -5260,6 +5261,7 @@ export default function ControlClient() {
                   value={input}
                   onChange={setInput}
                   onSubmit={handleEnhancedSubmit}
+                  onCanSubmitChange={setCanSubmitInput}
                   placeholder="Message the root agent… (paste files to upload)"
                 />
 
@@ -5268,7 +5270,8 @@ export default function ControlClient() {
                     <button
                       type="button"
                       onClick={() => enhancedInputRef.current?.submit()}
-                      className="flex items-center gap-2 rounded-xl bg-indigo-500/80 hover:bg-indigo-600 px-5 py-3 text-sm font-medium text-white transition-colors shrink-0"
+                      disabled={!canSubmitInput}
+                      className="flex items-center gap-2 rounded-xl bg-indigo-500/80 hover:bg-indigo-600 px-5 py-3 text-sm font-medium text-white transition-colors shrink-0 disabled:opacity-50 disabled:cursor-not-allowed disabled:hover:bg-indigo-500/80"
                     >
                       <ListPlus className="h-4 w-4" />
                       Queue
@@ -5286,7 +5289,8 @@ export default function ControlClient() {
                   <button
                     type="button"
                     onClick={() => enhancedInputRef.current?.submit()}
-                    className="flex items-center gap-2 rounded-xl bg-indigo-500 hover:bg-indigo-600 px-5 py-3 text-sm font-medium text-white transition-colors shrink-0"
+                    disabled={!canSubmitInput}
+                    className="flex items-center gap-2 rounded-xl bg-indigo-500 hover:bg-indigo-600 px-5 py-3 text-sm font-medium text-white transition-colors shrink-0 disabled:opacity-50 disabled:cursor-not-allowed disabled:hover:bg-indigo-500"
                   >
                     <Send className="h-4 w-4" />
                     Send

dashboard/src/components/enhanced-input.tsx

@@ -20,12 +20,14 @@ export interface SubmitPayload {
 
 export interface EnhancedInputHandle {
   submit: () => void;
+  canSubmit: () => boolean;
 }
 
 interface EnhancedInputProps {
   value: string;
   onChange: (value: string) => void;
   onSubmit: (payload: SubmitPayload) => void;
+  onCanSubmitChange?: (canSubmit: boolean) => void;
   placeholder?: string;
   disabled?: boolean;
   className?: string;
@@ -42,6 +44,7 @@ export const EnhancedInput = forwardRef<EnhancedInputHandle, EnhancedInputProps>
   value,
   onChange,
   onSubmit,
+  onCanSubmitChange,
   placeholder = "Message the root agent...",
   disabled = false,
   className,
@@ -307,10 +310,23 @@ export const EnhancedInput = forwardRef<EnhancedInputHandle, EnhancedInputProps>
     onChange('');
   }, [displayValue, lockedAgent, disabled, onSubmit, parsedAgentFromValue, value, onChange]);
 
+  // Check if submission is valid (has content or locked agent)
+  const canSubmit = useCallback(() => {
+    if (disabled) return false;
+    const trimmedValue = displayValue.trim();
+    return !!(trimmedValue || lockedAgent);
+  }, [disabled, displayValue, lockedAgent]);
+
+  // Notify parent when submission validity changes
+  useEffect(() => {
+    onCanSubmitChange?.(canSubmit());
+  }, [canSubmit, onCanSubmitChange]);
+
   // Expose submit method via ref so parent can trigger submit (e.g., from Send button)
   useImperativeHandle(ref, () => ({
     submit: handleSubmit,
-  }), [handleSubmit]);
+    canSubmit,
+  }), [handleSubmit, canSubmit]);
 
   const handleChange = (e: React.ChangeEvent<HTMLTextAreaElement>) => {
     const newValue = e.target.value;