fix(auth): add username option for basic auth in RunCommand

[OpeOginni]

Issue for this PR

Closes #

Related #25113

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

Added in remaining --username cli option to the opencode run --attach command. As this was also recently added to the Docs in another PR #25399

How did you verify your code works?

bun run typecheck

Screenshots / recordings

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[github-actions]

Thanks for your contribution!

This PR doesn't have a linked issue. All PRs must reference an existing issue.

Please:

1. Open an issue describing the bug/feature (if one doesn't exist)
2. Add Fixes #<number> or Closes #<number> to this PR description

See CONTRIBUTING.md for details.

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Based on my search, I found a potentially related PR:

Related PR

PR #25397: feat(opencode): add username option for basic auth in attach command with detailed docs
#25397

Why it's related: This PR also adds the username option for basic auth, but specifically for the attach command with documentation. Since PR #25600 is adding the --username option to the opencode run --attach command, these PRs appear to be addressing related or overlapping functionality. You may want to verify that both PRs don't conflict and coordinate the changes if needed.