[Feature]: Add support for API key helpers

[t3hk0d3]

1. Why Do You NEED This Feature?

In some environments API keys are ephemeral and requires some script to obtain/generate them.

For example if API key is rotated every X minutes and distributed using Hashicorp Vault.

In this case static API key is not an option.

2. What Is NOT Possible Right Now?

Currently its only possible to have static API key.

3. What WILL Be Possible With This Feature?

This will unlock coding when API keys are permanently rotated every X minutes (this is often used to avoid leaking API keys).

Proposed Solution (User Experience)

• Add option to specify script (bash/python/etc) to grab (generate/obtain) API key and emit it thru stdout.

Alternatives Considered

So far i've had to use local proxy that enriches all requests with ephemeral API key, but thats really unhandy.

Feature Category

AI/LLM Integration

Priority/Impact

Critical - Blocking my work

Examples from Other Tools

For example. Claude Code currently support this using apiKeyHelper (https://code.claude.com/docs/en/settings#available-settings)

Additional Context

No response

Pre-submission Checklist

• I have searched existing issues and confirmed this is not a duplicate
• I am willing to submit a PR to implement this feature