Add WebRTC ClientWindow to t2v app

[gtong-nv]

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[greptile-apps]

Greptile Summary

The PR adds persistent, prompt-driven WebRTC sessions to the v2 text-to-video runtime while keeping application state loaded between rollouts.

• Introduces explicit session-description requests and application-owned initialized defaults.
• Adds browser new_session events, persistent runner lifecycle handling, frame-generation flushing, and WebRTC reconnection.
• Updates T2V prompt resolution, integration usage, tests, and WebRTC documentation.

Confidence Score: 4/5

The stale-peer callback must be fixed before merging because it can terminate a newly reconnected browser session.

Reconnection permits a replacement peer while callbacks from the prior peer may still run, and those callbacks mutate shared connection state and enqueue a close event before checking peer identity.

Files Needing Attention: flashdreams/flashdreams/runtime_v2/serving/webrtc_server.py

Important Files Changed

Filename	Overview
flashdreams/flashdreams/runtime_v2/serving/webrtc_server.py	Adds reusable media-track generations and peer reconnection, but stale peer callbacks can disconnect a replacement client.
flashdreams/flashdreams/runtime_v2/session_runner.py	Adds replacement-session detection and coordinated session/window teardown while preserving windows between sessions.
flashdreams/flashdreams/runtime_v2/application_runner.py	Separates application initialization from sessions and adds persistent session serving.
flashdreams/flashdreams/t2v_v2/application.py	Allows prompts to come from per-session metadata while retaining an optional command-line default.
flashdreams/flashdreams/runtime_v2/serving/web/app.js	Adds prompt submission and retries WebRTC admission conflicts to support persistent serving.

Sequence Diagram

sequenceDiagram
  participant Browser
  participant Server as WebRTCServer
  participant Runner as ApplicationRunner
  participant Session
  Browser->>Server: Connect and open controls channel
  Browser->>Server: new_session(prompt)
  Server->>Runner: Buffered NewSession event
  Runner->>Session: create/init/run
  Session-->>Server: Video frames
  Server-->>Browser: WebRTC video
  Browser--xServer: Disconnect
  Runner->>Session: close
  Browser->>Server: Reconnect and request next session

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Comments Outside Diff (1)

1. flashdreams/flashdreams/runtime_v2/serving/webrtc_server.py, line 383-387 (link)

   Stale peer disconnects replacement

   When a replacement data channel opens before the old peer's terminal-state callback runs, this callback clears the shared connection state and queues a close event before _release_peer_connection rejects the stale peer, causing the newly connected session to stop.

   Knowledge Base Used: WebRTC Serving Flow

_{Reviews (1): Last reviewed commit: "Add persistent WebRTC sessions for v2 te..." | Re-trigger Greptile}