Pure, unit-tested core of the daemon-side relay that bridges the ab-connect
extension to the existing CdpClient. The extension exposes per-tab
chrome.debugger + synthesized Target events; CdpClient expects a browser-level
endpoint. So RelayState:
- answers Target.getTargets / attachToTarget / setDiscoverTargets LOCALLY from
targets learned via the extension's forwardCDPEvent(Target.attachedToTarget),
returning the extension's cb-tab-N sessionId (consumes those synth events
rather than double-forwarding them);
- forwards every other command as a forwardCDPCommand envelope (carrying
method/params/sessionId);
- maps forwardCDPCommand responses and forwardCDPEvent events back to raw CDP;
- validates the connect-handshake token; emits challenge/ping.
Keeps CdpClient and browser.rs unchanged. 8 unit tests; clippy clean. Still
inert — the tokio WS server + `connect` command wire it next.