terminal_view: Show hollow cursor when bar/underline is unfocused

[Dnreikronos]

Self-Review Checklist:**

• I've reviewed my own diff for quality, security, and reliability
• Unsafe blocks (if any) have justifying comments
• The content is consistent with the UI/UX checklist
• Tests cover the new/changed behavior
• Performance impact has been considered and is acceptable

What

When terminal cursor shape is set via escape sequences (e.g. \e[6 q for bar, \e[4 q for underline), the cursor looks identical whether the terminal is focused or unfocused. Block cursors already convert to a hollow outline when unfocused, but bar and underline were missing this treatment.

How

Added unfocused guards for Beam and Underline in the cursor shape match in terminal_element.rs, converting them to Hollow when the terminal loses focus. This follows the same pattern already used for Block.

Why this approach

A hollow block outline is the clearest unfocused signal and stays consistent with the existing Block behavior. Alternative approaches like dimming opacity or drawing outlined versions of bar/underline were considered, but a 2px-wide outlined bar would be nearly invisible at normal font sizes.

Demo:

Before:

terminal_focus.mp4

After:

terminal_focus_after.mp4

Closes #52716

Release Notes:

• Fixed terminal bar and underline cursors set via escape sequences not visually distinguishing between focused and unfocused states