Module webview/agentChat/bridgeClient

Webview-side IAgentRuntimesClient implementation that proxies every call to the extension host via postMessage.

The extension host listens with AgentChatBridgeHandler and answers with a response envelope correlated by request ID. This file exposes:

• BridgeAgentRuntimesClient — the IAgentRuntimesClient implementation used inside the Agent Chat webview.
• createBridgeTransport — factory that wires the VS Code postMessage plumbing and returns a typed request function used by the class.

Phase 2b scope: request/response only. Streaming support (for streamChat) lands in a follow-up phase when the SDK grows typed streaming methods.