feat(speaking): add getDialogueDefaults service helper

src/services/speaking.ts

@@ -103,3 +103,22 @@ export async function generateClassSummary(
   })
   return parse<ClassSummaryResponse>(res)
 }
+
+export interface DialogueModeDefaults {
+  systemPrompt: string
+  greeting: string
+}
+
+export interface DialogueDefaultsResponse {
+  videoScene: DialogueModeDefaults
+  nonVideoScene: DialogueModeDefaults
+}
+
+export async function getDialogueDefaults(): Promise<DialogueDefaultsResponse> {
+  const res = await fetch(`${DIALOGUE_BASE}/defaults`, {
+    method: 'GET',
+    headers: { 'Content-Type': 'application/json' },
+    credentials: 'include',
+  })
+  return parse<DialogueDefaultsResponse>(res)
+}