Expose a side-effect-free credentials entrypoint

[kamilio]

Problem

Credential helpers are currently available only through a broad package entrypoint that also initializes unrelated functionality. Lightweight consumers need a supported way to read credentials without importing the full application surface.

Requested capability

Add a narrow, side-effect-free package export for the existing credential helpers and their public types.

Acceptance criteria

• The subpath is included in package exports and published artifacts.
• Importing it performs no UI setup, output, browser launch, or unrelated application initialization.
• Existing credential precedence and error behavior remain unchanged.
• Packed-package tests cover the subpath on supported Node versions.

[kamilio]

Resolved by ee8113f, with the CI stabilization in bc9ccac. Released successfully via https://github.com/poe-platform/poe-code/actions/runs/29855049561.