fix: add support for DAILY_SAMPLE_ROOM_URL when calling /start for DailyTransport

Author: markbackman

CHANGELOG.md

@@ -28,6 +28,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Fixed an issue in `ServiceSwitcher` where the `STTService`s would result in
   all STT services producing `TranscriptionFrame`s.
+- Fixed an issue in the runner where starting a DailyTransport room via
+  `/start` didn't support using the `DAILY_SAMPLE_ROOM_URL` env var.
 
 ## [0.0.91] - 2025-10-21