feat(tasks): Add model info as part of metadata

[shantur]

What does this PR do?

Adds model info as part of tasks tool metadata

How did you verify your code works?

• Create a session with Tasks tool using cli
• Ran opencode serve and used curl to confirm metadata in json API

[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]

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No duplicate PRs found