feat(site): add cmd+enter to submit tasks immediately (#21182)

Implements cmd+enter (Mac) / ctrl+enter (Windows/Linux) keyboard
shortcut for submitting tasks on the tasks page. Regular enter key still
creates new lines as expected.

Fixes #21179

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>

site/src/modules/tasks/TaskPrompt/TaskPrompt.tsx

@@ -216,7 +216,7 @@ const CreateTaskForm: FC<CreateTaskFormProps> = ({ templates, onSuccess }) => {
 		},
 	});
 
-	const onSubmit = async (e: React.FormEvent<HTMLFormElement>) => {
+	const onSubmit = async (e: React.SyntheticEvent) => {
 		e.preventDefault();
 
 		try {
@@ -231,6 +231,13 @@ const CreateTaskForm: FC<CreateTaskFormProps> = ({ templates, onSuccess }) => {
 		}
 	};
 
+	const handleKeyDown = (e: React.KeyboardEvent<HTMLTextAreaElement>) => {
+		// Submit form on Cmd+Enter (Mac) or Ctrl+Enter (Windows/Linux)
+		if (e.key === "Enter" && (e.metaKey || e.ctrlKey)) {
+			onSubmit(e);
+		}
+	};
+
 	return (
 		<form
 			onSubmit={onSubmit}
@@ -259,6 +266,7 @@ const CreateTaskForm: FC<CreateTaskFormProps> = ({ templates, onSuccess }) => {
 					onChange={(e) => setPrompt(e.target.value)}
 					readOnly={isPromptReadOnly}
 					isSubmitting={createTaskMutation.isPending}
+					onKeyDown={handleKeyDown}
 				/>
 				<div className="flex items-center justify-between pt-2">
 					<div className="flex items-center gap-1">