why

• this allows users to specify a CDP url that the extension will use for its loopback/in-browser connection

what changed

• exposed ExtensionCDPURL in LocalBrowserConnectOptions

test plan

• added unit tests ensuring the URL gets correctly propagated through the protocol

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Summary by cubic

Adds an optional ExtensionCDPURL field to LocalBrowserConnectOptions in the Go SDK, letting users set the CDP WebSocket URL the extension uses for its in-browser connection independently of the client's CDP URL. When empty, the client's CDP URL is used as before.

• Validates ExtensionCDPURL is a ws:// or wss:// URL with a valid host and port before connecting (including rejecting port 0).
• Propagates the URL to the extension init; falls back to the client's CDP URL when unset.
• Includes unit tests for validation and propagation.