Per-method default timeout on transports

[u9g]

Is your feature request related to a problem? Please describe.
I set per-RPC deadlines from a custom method option in my protos (deadline_ms), so a slow RPC like an upload gets minutes and everything else gets 10 seconds. defaultTimeoutMs (#799) only takes one number for the whole transport, and an interceptor can't help because the deadline signal is already made from timeoutMs before the interceptors run.

Today I wrap the Transport to fill in the timeout myself:

function withDeadlines(transport: Transport): Transport {
  return {
    unary: (method, signal, timeoutMs, header, input, contextValues) =>
      transport.unary(method, signal, timeoutMs ?? deadline(method), header, input, contextValues),
    stream: (method, signal, timeoutMs, header, input, contextValues) =>
      transport.stream(method, signal, timeoutMs ?? deadline(method), header, input, contextValues),
  };
}

It works, but it restates the Transport signatures and sits outside the options where the timeout default lives.

Describe the solution you'd like
Let defaultTimeoutMs also take a function of the method, for both Connect for Web and Connect for Node.js:

createConnectTransport({
  baseUrl,
  defaultTimeoutMs: (method: DescMethod) =>
    hasOption(method, deadline_ms) ? getOption(method, deadline_ms) : 10_000,
});

A per-call timeoutMs still wins, and <= 0 still means no timeout. The change would be the type in CommonTransportOptions and the web/node transport options, plus resolving the value in the places that read opt.defaultTimeoutMs today (the three protocol transports in @connectrpc/connect/protocol-* and the two in @connectrpc/connect-web). Widening the option type is backward compatible for anyone passing a number.

Describe alternatives you've considered

• Let interceptors set the call's timeout. That needs the deadline signal to be created after the interceptors run, which is a much bigger change to runUnaryCall/runStreamingCall.
• Keep wrapping the Transport, as above.

If this shape sounds fine, I'm happy to send the PR with tests and docs.