Show the whole option preview on native so every line is reachable

On Android, a slow drag inside a preview capped at 240px did not scroll
it, so lines past the cap could not be read. The preview's nested
scroll sits inside the option's Pressable; the same drag scrolls it
once the preview is outside the Pressable. Native now renders the
preview at full height so the chat scroll reaches every line, and a tap
on it still selects the option. Web keeps the 240px cap.

The mock agent's rollout preview is now taller than the cap so the
Android replay can check the last line.

packages/server/src/server/agent/providers/mock-load-test-agent.ts

@@ -278,6 +278,8 @@ const ROLLOUT_FLAG_PREVIEW = [
   'if (flags.enabled("new-surface")) {',
   "  render(<NewSurface />);",
   "}",
+  ...Array.from({ length: 40 }, (_, i) => `// rollout step ${i + 1}`),
+  "// LAST PREVIEW LINE",
 ].join("\n");
 
 function parseMockQuestionPrompt(prompt: AgentPromptInput): MockQuestionPromptRequest | null {