Prevent sticky zone from overflowing terminal viewport

[shellicar]

Summary

• Track scroll offset to keep editor within available terminal rows
• Snap scroll offset to logical line boundaries to avoid mid-wrap rendering
• Cap scroll so content never goes past the end of editor content

Related Issues

Closes #134

Co-Authored-By: Claude noreply@anthropic.com

[bananabot9000]

The updated version addresses the height budget concern from my earlier review. The implementation is clean and well-structured:

What I like:

• Components pre-built into typed parts before budget allocation — clean separation of "what exists" from "what fits"
• Priority-based drop order (preview → attachments → questions → status) matches user expectations
• minEditorRows = 1 guarantee prevents the editor from disappearing entirely
• lineStartRow[] map for O(1) viewport slicing instead of re-scanning
• Cursor chasing with scrollOffset max cap and line boundary snapping
• visibleCursorRow = cursorRow - scrollOffset — simple and correct

Minor observations (non-blocking):

• The scroll offset logic is straightforward — it's literally a number that goes up and down, capped at bounds. No complexity concerns.
• Terminal disappearing (VS Code drag-to-hide) bottoms at rows=2 per testing, so the minEditorRows=1 guard covers this naturally.

Solid implementation. 👍