Enable Multi-line Input for Agent Description Field

[Fahleen1]

Summary

#11104 Update AgentConfig to use textarea for description and adjust input class.

Change Type

Please delete any irrelevant options.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Checklist

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• My code adheres to this project's style guidelines
• I have performed a self-review of my own code
• My changes do not introduce new warnings

[Copilot]

Pull request overview

This PR converts the Agent Description field from a single-line <input> to a multi-line <textarea> element, enabling users to provide detailed multi-line guidance for agents. The change addresses issue #11104, which identified that while the display UI already supports multi-line text with whitespace-pre-wrap, the input UI was limited to single-line input.

Changes:

• Modified the description field from <input type="text"> to <textarea> element
• Added resize-none class to the shared inputClass constant to prevent textarea resizing
• Removed the type="text" attribute (not applicable to textarea elements)

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