feat(gateway): centralize audio routing + FLAC support + Telegram doc fallback (#17833)

Extracted from PR #17211 (@versun) so it can land independently of the
local_command TTS provider redesign.

- Add should_send_media_as_audio(platform, ext, is_voice) in
  gateway/platforms/base.py; single source of truth for audio routing.
- Add .flac to recognized audio extensions (MEDIA regex, weixin audio
  set, send_message audio set).
- Telegram send_voice() now falls back to send_document for formats
  Telegram's Bot API can't play natively (.wav, .flac, ...) instead of
  raising; MP3/M4A still go to sendAudio, Opus/OGG still go to sendVoice.
- Route _send_telegram() in send_message_tool through a narrower
  _TELEGRAM_SEND_AUDIO_EXTS = {.mp3, .m4a} set.
- cron.scheduler._send_media_via_adapter now delegates the audio
  decision to should_send_media_as_audio so it matches the gateway.
- Update the cron live-adapter ogg test to flag [[audio_as_voice]] so
  it still routes to sendVoice under the new Telegram-specific policy.
- Tests: unit coverage for should_send_media_as_audio across platforms,
  end-to-end MEDIA routing via _process_message_background and
  GatewayRunner._deliver_media_from_response, TelegramAdapter.send_voice
  fallback for FLAC/WAV.

Co-authored-by: Versun <me+github7604@versun.org>

cron/scheduler.py

@@ -277,13 +277,21 @@ def _resolve_delivery_target(job: dict) -> Optional[dict]:
     return targets[0] if targets else None
 
 
-# Media extension sets — keep in sync with gateway/platforms/base.py:_process_message_background
-_AUDIO_EXTS = frozenset({'.ogg', '.opus', '.mp3', '.wav', '.m4a'})
+# Media extension sets — audio routing is centralized in gateway.platforms.base
+# via should_send_media_as_audio() so Telegram-specific rules stay in one place.
 _VIDEO_EXTS = frozenset({'.mp4', '.mov', '.avi', '.mkv', '.webm', '.3gp'})
 _IMAGE_EXTS = frozenset({'.jpg', '.jpeg', '.png', '.webp', '.gif'})
 
 
-def _send_media_via_adapter(adapter, chat_id: str, media_files: list, metadata: dict | None, loop, job: dict) -> None:
+def _send_media_via_adapter(
+    adapter,
+    chat_id: str,
+    media_files: list,
+    metadata: dict | None,
+    loop,
+    job: dict,
+    platform=None,
+) -> None:
     """Send extracted MEDIA files as native platform attachments via a live adapter.
 
     Routes each file to the appropriate adapter method (send_voice, send_image_file,
@@ -292,10 +300,13 @@ def _send_media_via_adapter(adapter, chat_id: str, media_files: list, metadata:
     """
     from pathlib import Path
 
+    from gateway.platforms.base import should_send_media_as_audio
+
     for media_path, _is_voice in media_files:
         try:
             ext = Path(media_path).suffix.lower()
-            if ext in _AUDIO_EXTS:
+            route_platform = platform if platform is not None else getattr(adapter, "platform", None)
+            if should_send_media_as_audio(route_platform, ext, is_voice=_is_voice):
                 coro = adapter.send_voice(chat_id=chat_id, audio_path=media_path, metadata=metadata)
             elif ext in _VIDEO_EXTS:
                 coro = adapter.send_video(chat_id=chat_id, video_path=media_path, metadata=metadata)
@@ -444,7 +455,15 @@ def _deliver_result(job: dict, content: str, adapters=None, loop=None) -> Option
 
                 # Send extracted media files as native attachments via the live adapter
                 if adapter_ok and media_files:
-                    _send_media_via_adapter(runtime_adapter, chat_id, media_files, send_metadata, loop, job)
+                    _send_media_via_adapter(
+                        runtime_adapter,
+                        chat_id,
+                        media_files,
+                        send_metadata,
+                        loop,
+                        job,
+                        platform=platform,
+                    )
 
                 if adapter_ok:
                     logger.info("Job '%s': delivered to %s:%s via live adapter", job["id"], platform_name, chat_id)