fix(speech): surface streaming playback compatibility

packages/ui/src/lib/speech-playback-support.ts

@@ -0,0 +1,58 @@
+import type { SpeechCapabilitiesResponse } from "../../../server/src/api-types"
+import type { SpeechPlaybackMode, SpeechTtsFormat } from "../stores/preferences"
+
+export interface SpeechPlaybackSupportResult {
+  available: boolean
+  reason?: "unsupported-environment" | "provider-streaming-unavailable" | "browser-streaming-unavailable"
+}
+
+export function formatToMimeType(format: SpeechTtsFormat): string {
+  if (format === "wav") return "audio/wav"
+  if (format === "opus") return getSupportedMimeType(format)
+  if (format === "aac") return "audio/aac"
+  return "audio/mpeg"
+}
+
+export function getCandidateMimeTypes(format: SpeechTtsFormat): string[] {
+  if (format === "wav") return ["audio/wav"]
+  if (format === "opus") {
+    return ['audio/ogg; codecs="opus"', 'audio/webm; codecs="opus"', "audio/opus"]
+  }
+  if (format === "aac") return ["audio/aac", "audio/mp4", 'audio/mp4; codecs="mp4a.40.2"']
+  return ["audio/mpeg"]
+}
+
+export function getSupportedMimeType(format: SpeechTtsFormat): string {
+  const candidates = getCandidateMimeTypes(format)
+  if (typeof MediaSource === "undefined") {
+    return candidates[0]
+  }
+  return candidates.find((candidate) => MediaSource.isTypeSupported(candidate)) ?? candidates[0]
+}
+
+export function getSpeechPlaybackSupport(options: {
+  playbackMode: SpeechPlaybackMode
+  ttsFormat: SpeechTtsFormat
+  capabilities?: SpeechCapabilitiesResponse | null
+}): SpeechPlaybackSupportResult {
+  if (typeof window === "undefined" || typeof window.Audio === "undefined") {
+    return { available: false, reason: "unsupported-environment" }
+  }
+
+  if (options.playbackMode !== "streaming") {
+    return { available: true }
+  }
+
+  if (!options.capabilities?.supportsStreamingTts) {
+    return { available: false, reason: "provider-streaming-unavailable" }
+  }
+
+  if (
+    typeof MediaSource === "undefined" ||
+    !getCandidateMimeTypes(options.ttsFormat).some((candidate) => MediaSource.isTypeSupported(candidate))
+  ) {
+    return { available: false, reason: "browser-streaming-unavailable" }
+  }
+
+  return { available: true }
+}