Summary

• Tightens the outline button style to improve contrast and visibility.
• Makes prompt enhancements visible in the composer and reversible by storing the original prompt state.
• Adds pinned preview tabs with pin/unpin controls and prevents pinned tabs from being closed directly.
• Adds a configurable code font size override for editor and terminal rendering.

Testing

• Not run (PR content only).
• Existing and new unit tests were added for prompt enhancement state, preview tab pinning, and related behavior.
• No manual verification was performed in this step.