[Bug] Wide markdown tables render with overlapping rows and misaligned borders on resize

Bug Description

Title: Wide markdown tables render broken — overlapping/duplicated rows and misaligned borders

Description:
Wide markdown tables (~6+ columns) do not render responsively. At certain terminal widths, the table misaligns, truncates mid-cell, collapses into a stacked layout, or disappears entirely at full screen.

During streaming, stale partial renders are not cleared properly. This causes rows and borders to overlap or appear duplicated (see screenshot). Resizing the terminal, especially narrowing it, can temporarily fix the issue, suggesting a width calculation and redraw clearing bug.

Repro:

1. Generate a markdown table with ~6+ columns and long cell content.
2. Observe while it streams or resize the terminal.
3. Rows overlap, duplicate, and borders break.

Expected:

• Table renders cleanly and stays aligned at all widths.
• Previous frames are cleared properly during redraw.

Actual:

• Rows overlap or duplicate.
• Borders become misaligned or broken.
• Table may disappear at certain widths.

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Environment Info

• Platform: darwin
• Terminal: xterm-256color
• Version: 2.1.160
• Feedback ID: 648b8dc6-1dbb-47fe-b20a-80e4871c054f

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Errors

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