feat(llms): add transformRequestBody hook and improve prompt assembly (#480)

* feat(llms): add transformRequestBody hook and refine prompt handling

* docs(website): document transformRequestBody usage

* refactor(extension): keep function-valued config handling consistent in useAgent

* feat: simplify `transformRequestBody`

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Co-authored-by: Simon <10131203+gaomeng1900@users.noreply.github.com>

packages/extension/src/components/cards.tsx

@@ -146,6 +146,7 @@ function CopyButton({ text, label }: { text: string; label: string }) {
 function extractPrompt(rawRequest: unknown, role: 'system' | 'user'): string | null {
 	const messages = (rawRequest as { messages?: { role: string; content?: unknown }[] })?.messages
 	if (!messages) return null
+	if (!Array.isArray(messages)) return null
 	const msg =
 		role === 'system'
 			? messages.find((m) => m.role === role)