Summary

Color emoji glyphs are placed slightly toward the upper-right of their 2-cell terminal slot instead of being centered, and the glyph bitmap does not visually fill the 2 cells it advances.

Steps to reproduce

1. Use a config that maps emoji to a color-emoji family, e.g.:

   [fonts]
   size = 20
   family = "UDEV Gothic"
   
   [[fonts.symbol-map]]
   start = "1F300"
   end   = "1FAFF"
   font-family = "Segoe UI Emoji"

2. Run echo a👍a in any shell.

Expected

The 👍 sits centered in its 2-cell slot, baseline aligned with the surrounding a characters.

Actual

The emoji is shifted up and slightly right; the right half of the 2-cell slot looks empty.

Environment

• Rio version: 0.4.0 (commit 97340fe, branch main)
• OS: Windows 11 Pro 26200
• Primary font: UDEV Gothic 20pt
• Emoji font: Segoe UI Emoji (via [[fonts.symbol-map]])
• Shell: pwsh.exe 7.6