Tasks: GitHub external auth enforced even when removed from template version #20315

Bug Report

Description

When creating a task from a template version where data "coder_external_auth" has been removed, the UI still prompts users to "Connect to GitHub" and blocks task creation.

Expected Behavior

If there is no data "coder_external_auth" block in the template, the system should not enforce GitHub login for task creation.

Actual Behavior

The system appears to check for external auth in the active version rather than respecting the configuration in the specific template version being used. This causes the "Connect to GitHub" prompt to appear even when external auth has been removed.

Steps to Reproduce

1. Create a template with GitHub external auth configured
2. Create a new version of the template with the data "coder_external_auth" block removed
3. Attempt to create a task from the new version
4. Observe that the UI still prompts to connect to GitHub

Impact

This blocks users from testing Tasks with templates that don't require external auth. Workaround is to create a template copy.

Additional Context

Reported in internal Slack discussion. Screenshot shows the "Connect to GitHub" prompt appearing when it shouldn't.