refactor: share speech normalization helpers

src/plugin-sdk/speech-core.ts

@@ -3,4 +3,10 @@
 export type { SpeechProviderPlugin } from "../plugins/types.js";
 export type { SpeechVoiceOption } from "../tts/provider-types.js";
 
-export { parseTtsDirectives } from "../tts/tts-core.js";
+export {
+  normalizeApplyTextNormalization,
+  normalizeLanguageCode,
+  normalizeSeed,
+  parseTtsDirectives,
+  requireInRange,
+} from "../tts/tts-core.js";