feat: implement <Kbd /> and shortcut tooltip (#21971)

Closes #21650

This pull-request adds a `<Tooltip />` with `<Kbd />` modifiers to the
`Run Task` button describing the shortcut how to submit the prompt
quickly without having to navigate to the `↑` button.

<img width="456" height="298" alt="CleanShot 2026-02-06 at 19 40 58@2x"
src="https://github.com/user-attachments/assets/fa08a373-21c3-4620-9551-0c8a6b3547ab"
/>

It should be noted that the [keyboard shortcut already
existed](https://github.com/coder/coder/blob/jakehwll/21650-submit-prompt-shortcut/site/src/modules/tasks/TaskPrompt/TaskPrompt.tsx#L222-L227)
so we don't need to implement that here.

```ts
	// L222-L227
	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);
		}
	};
```

---------

Co-authored-by: Danielle Maywood <danielle@themaywoods.com>

site/src/components/Kbd/Kbd.stories.tsx

@@ -0,0 +1,43 @@
+import type { Meta, StoryObj } from "@storybook/react-vite";
+import { CommandIcon } from "lucide-react";
+import { Kbd, KbdGroup } from "./Kbd";
+
+const meta: Meta<typeof Kbd> = {
+	title: "components/Kbd",
+	component: Kbd,
+	args: {
+		children: "K",
+	},
+};
+
+export default meta;
+type Story = StoryObj<typeof Kbd>;
+
+export const Default: Story = {};
+
+export const WithIcon: Story = {
+	args: {
+		children: <CommandIcon />,
+	},
+};
+
+export const Group: Story = {
+	render: () => (
+		<KbdGroup>
+			<Kbd>
+				<CommandIcon />
+			</Kbd>
+			<Kbd>Enter</Kbd>
+		</KbdGroup>
+	),
+};
+
+export const MultipleKeys: Story = {
+	render: () => (
+		<KbdGroup>
+			<Kbd>Ctrl</Kbd>
+			<Kbd>Shift</Kbd>
+			<Kbd>P</Kbd>
+		</KbdGroup>
+	),
+};

site/src/components/Kbd/Kbd.tsx

@@ -0,0 +1,27 @@
+import { cn } from "utils/cn";
+
+function Kbd({ className, ...props }: React.ComponentProps<"kbd">) {
+	return (
+		<kbd
+			data-slot="kbd"
+			className={cn(
+				"inline-flex items-center justify-center gap-1",
+				"h-5 w-fit min-w-5 font-sans text-xs font-medium select-none",
+				"bg-surface-tertiary text-content-secondary rounded-sm px-1",
+				"[&_svg:not([class*='size-'])]:size-3 pointer-events-none",
+				className,
+			)}
+			{...props}
+		/>
+	);
+}
+function KbdGroup({ className, ...props }: React.ComponentProps<"div">) {
+	return (
+		<kbd
+			data-slot="kbd-group"
+			className={cn("gap-1 inline-flex items-center", className)}
+			{...props}
+		/>
+	);
+}
+export { Kbd, KbdGroup };

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

@@ -11,6 +11,7 @@ import { ErrorAlert } from "components/Alert/ErrorAlert";
 import { Button } from "components/Button/Button";
 import { ExternalImage } from "components/ExternalImage/ExternalImage";
 import { displayError, displaySuccess } from "components/GlobalSnackbar/utils";
+import { Kbd, KbdGroup } from "components/Kbd/Kbd";
 import { Link } from "components/Link/Link";
 import {
 	Select,
@@ -34,6 +35,7 @@ import TextareaAutosize, {
 	type TextareaAutosizeProps,
 } from "react-textarea-autosize";
 import { docs } from "utils/docs";
+import { getOSKey } from "utils/platform";
 import { PromptSelectTrigger } from "./PromptSelectTrigger";
 import { TemplateVersionSelect } from "./TemplateVersionSelect";
 
@@ -373,23 +375,34 @@ const CreateTaskForm: FC<CreateTaskFormProps> = ({ templates, onSuccess }) => {
 							/>
 						)}
 
-						<Button
-							size="icon"
-							type="submit"
-							disabled={prompt.trim().length === 0 || isMissingExternalAuth}
-							className="rounded-full disabled:bg-surface-invert-primary disabled:opacity-70"
-						>
-							<Spinner
-								loading={
-									isLoadingExternalAuth ||
-									isPollingExternalAuth ||
-									createTaskMutation.isPending
-								}
-							>
-								<ArrowUpIcon />
-							</Spinner>
-							<span className="sr-only">Run task</span>
-						</Button>
+						<Tooltip>
+							<TooltipTrigger asChild>
+								<Button
+									size="icon"
+									type="submit"
+									disabled={prompt.trim().length === 0 || isMissingExternalAuth}
+									className="rounded-full disabled:bg-surface-invert-primary disabled:opacity-70"
+								>
+									<Spinner
+										loading={
+											isLoadingExternalAuth ||
+											isPollingExternalAuth ||
+											createTaskMutation.isPending
+										}
+									>
+										<ArrowUpIcon />
+									</Spinner>
+									<span className="sr-only">Run task</span>
+								</Button>
+							</TooltipTrigger>
+							<TooltipContent align="end">
+								<KbdGroup>
+									<Kbd>{getOSKey()}</Kbd>
+									<span>+</span>
+									<Kbd>Enter</Kbd>
+								</KbdGroup>
+							</TooltipContent>
+						</Tooltip>
 					</div>
 				</div>
 			</fieldset>

site/src/utils/platform.ts

@@ -0,0 +1,14 @@
+/**
+ * Returns true if the current platform is macOS.
+ */
+function isMac(): boolean {
+	return !!navigator.platform.match("Mac");
+}
+
+/**
+ * Returns the platform-appropriate modifier key label: ⌘ on macOS,
+ * Ctrl on everything else.
+ */
+export function getOSKey(): string {
+	return isMac() ? "⌘" : "Ctrl";
+}