Fix double-width line (DECDWL / ESC #6) fragment positioning

[epatel]

Summary

• The old moveTopLeft(textScale.inverted().map(textArea.topLeft())) inverse-mapped the entire top-left point (margins + column offset), so the painter's scale(2,1) simply recovered the original single-width coordinates
• On lines with multiple text fragments (e.g. box-drawing chars + text + box-drawing chars), each fragment was placed at its single-width position but rendered at double width, causing overlaps and gaps
• Fix: inverse-map only the margin/origin offset and leave the column position unmapped, so the painter scale correctly doubles it

Test script

#!/usr/bin/env bash
# Test ESC #6 (DECDWL - double-width line) rendering
# On a correct terminal, the boxes should be the same width

clear
printf '\033[H'

# Normal width box (20 chars wide)
printf '\033#5'
printf '\033(0lqqqqqqqqqqqqqqqqqqk\033(B\n'
printf '\033#5'
printf '\033(0x\033(B  Normal width    \033(0x\033(B\n'
printf '\033#5'
printf '\033(0mqqqqqqqqqqqqqqqqqqj\033(B\n'

printf '\n'

# Double width box (10 chars = 20 screen columns)
printf '\033#6'
printf '\033(0lqqqqqqqqk\033(B\n'
printf '\033#6'
printf '\033(0x\033(B Double \033(0x\033(B\n'
printf '\033#6'
printf '\033(0mqqqqqqqqj\033(B\n'

printf '\n\033#5'
printf 'If both boxes are the same width, ESC #6 works correctly.\n'
printf 'If the double box is narrower, spaces are not being doubled.\n'

Test plan

• Run the test script above — both boxes should be the same screen width
• Verify box-drawing characters on double-width lines render as solid lines (no dashed gaps)
• Verify normal (non-double-width) text rendering is unaffected

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