Agent Skills: Implement Specialized Blue-Themed UI for Skill Activations

[NTaylorMullen]

Enhance the visual representation of skill activations in the chat UI. Skill-related actions should be visually distinguished from standard tool calls to signify a structural change in the agent's capabilities.

Requirements:

• Thematic Styling: Adopt theme.text.link (blue) as the primary accent color for skill-related UI elements.
• Custom Tool Rendering: Update ToolShared.tsx and ToolGroupMessage.tsx to implement a refined UI for activate_skill.
• Iconography: Use a dedicated "Star" icon (🌟) in the tool call header to represent specialized expertise activation.
• Clean Headers: Implement a concise header format: Activate Skill "name": description, removing any redundant system prefixes.

Part of #15327

[NTaylorMullen]

Decided against implementing a specialized UI theme for skill activations to keep the interface consistent.