Allow passing a custom timeout to opencode run

[AurelienRibon]

Some models, like gpt-5-pro, can think for way longer than the default 5 minutes timeout.
This PR allows the customization of this parameter, with a new --timeout argument passed to opencode run.

Does it work?

With a small timeout, we get a TimeoutError from fetch, as expected.

With a sufficient timeout, no error.

Without any custom timeout, no error.

EDIT

I just added support for timeout units (like --timeout 60s). If no unit is provided, ms is assumed.

[AurelienRibon]

I changed the proposition to a constant-based approach, which is less intrusive (does not appear in help, does not introduce new params to existing functions).

This PR is still required for gpt-5-pro to work, as the current state of the tool prevents the model from completing its work (most complex questions require ~10mins to complete, some can go to 20mins).

[rekram1-node]

Do u still think this makes sense even with OPENCODE_CONFIG, OPENCODE_CONFIG_CONTENT, and existing opencode configs that let u specify timeout?

[rekram1-node]

@AurelienRibon okay someone else asked for it: #3583

Can we make it a flag for the run command and drop the env var?

[AurelienRibon]

@rekram1-node hey, sorry I took a day off with the wife and kid. I initially made it a flag, so I will just roll-back the latest changes to restore the flag behavior. Will do that tomorrow, you'll tell me if the result is fine.

Only question I had in my mind when it was a CLI argument: what should it be named? I chose --timeout initially for simplicity, but that could be ambiguous, as it's the timeout for one model request, not the entire opencode run loop. I'll go with --timeout, but if you have a better idea in the meantime, just say.

[rekram1-node]

timeout is good, and hey no worries dont worry about being super responsive family takes priority and u are doing this for fun hope im not coming off as needing u to do things immediately! :)

[AurelienRibon]

All done, I updated the PR description with new behavior examples.

[AurelienRibon]

@actions-user, why you create conflicts?