refactor: route plugin runtime through bundled seams

extensions/speech-core/runtime-api.ts

@@ -0,0 +1,33 @@
+export {
+  buildTtsSystemPromptHint,
+  getLastTtsAttempt,
+  getResolvedSpeechProviderConfig,
+  getTtsMaxLength,
+  getTtsProvider,
+  isSummarizationEnabled,
+  isTtsEnabled,
+  isTtsProviderConfigured,
+  listSpeechVoices,
+  maybeApplyTtsToPayload,
+  resolveTtsAutoMode,
+  resolveTtsConfig,
+  resolveTtsPrefsPath,
+  resolveTtsProviderOrder,
+  setLastTtsAttempt,
+  setSummarizationEnabled,
+  setTtsAutoMode,
+  setTtsEnabled,
+  setTtsMaxLength,
+  setTtsProvider,
+  synthesizeSpeech,
+  textToSpeech,
+  textToSpeechTelephony,
+  _test,
+  type ResolvedTtsConfig,
+  type ResolvedTtsModelOverrides,
+  type TtsDirectiveOverrides,
+  type TtsDirectiveParseResult,
+  type TtsResult,
+  type TtsSynthesisResult,
+  type TtsTelephonyResult,
+} from "./src/tts.js";