`thv proxy` process might hang indefinitely with active client connections

[danbarr]

Reproduce:

1. Start a thv proxy process
2. Make at least one client connection thru the proxy
3. Attempt to stop the proxy with Ctrl-C

^C1:43PM INF Received signal interrupt, stopping proxy...

<nothing happens>

Result: proxy process doesn't stop after the first attempt (probably expected since we're sending SIGINT and not SIGKILL)

But, subsequent Ctrl-C don't stop the process, it waits until all client connections are closed, which is not always obvious how to do other than completely closing IDEs (for example with Roo Code, just disabling the server doesn't work, seems you have to disable AND refresh it to actually close the existing connection - or completely close all VS Code windows).

Can/should we make a second Ctrl-C send SIGKILL?