Playwright tunnel stop can hang while waiting for connection

[justinTM]

Summary

PlaywrightTunnel.stopAsync() can hang when the tunnel is stopped while it is still waiting for a poll-connection client to arrive.

Why this is a separate issue

The current PR (#5851) fixes a Start/Stop lifecycle race by waiting for an in-progress stop before starting again. That does not address the case where Stop itself never settles while the tunnel is still in waiting-for-connection / poll-connection mode.

Suspected root cause

In poll-connection mode, _pollConnectionAsync() returns a promise that only resolves after a WebSocket connection succeeds. stopAsync() clears the polling interval, but it still awaits _initWsPromise, which can remain unresolved forever if Stop happens before a connection arrives.

Proposed fix shape

• Add a cancellation/settle path for the pending poll promise when stopping.
• Ensure stopAsync() can complete even if no WebSocket ever connected.
• Clear any pending poll state and set status to stopped as part of stop teardown.

Evidence

A local gws auth login flow now reaches a clean timeout when the VS Code extension never connects, which suggests the remaining stall is in the extension stop path rather than the remote side.