Background audio no longer republished after reconnect

Patch Changes

• fix: do not republish background audio tracks after reconnect - #1487 (@davidzhao)

• Fail download-files when plugin downloads fail - #1481 (@toubatbrian)

• chore(amd): update default models and drop null support - #1476 (@chenghao-mou)

• Add TTS pronunciation customization support to agents, Google Gemini TTS, and Sarvam TTS. - #1473 (@rosetta-livekit-bot)

• chore(amd): add default amd prediction log - #1496 (@chenghao-mou)

• Add TTS text transforms with built-in markdown/emoji filtering, streaming replacement, and custom callable transform support. - #1477 (@rosetta-livekit-bot)