## What happened

Running `omarchy font set <name>` resets the foot terminal's font size back
to `9`, discarding whatever size was previously set (e.g. via
`omarchy display text size <px>`).

This is specific to foot. For alacritty, kitty, and ghostty, `omarchy-font-set`
only rewrites the font *family* and leaves the size line untouched. But for
foot it rewrites the whole directive with a hardcoded size:

```bash
if [[ -f ~/.config/foot/foot.ini ]]; then
  sed -i "s/^font=.*/font=$font_name:size=9/g" ~/.config/foot/foot.ini
fi
```

(from `omarchy-font-set`, the binary behind `omarchy font set`)

## Expected

Changing the font family should not change the font size on any terminal.
Foot should behave like the other three: preserve the existing `:size=N`
suffix and only swap the family.

## Steps to reproduce

```bash
omarchy display text size 14   # sets foot.ini to font=<Family>:size=11
omarchy font set "JetBrainsMono Nerd Font"
grep '^font=' ~/.config/foot/foot.ini
# => font=JetBrainsMono Nerd Font:size=9   (size silently reverted; expected size=11)
```

## System

- Omarchy version: 4.0.1-1
- Kernel: Linux 7.1.9-arch1-2 x86_64
- Terminal: foot

## Suggested fix

Preserve the existing size instead of hardcoding it:

```bash
if [[ -f ~/.config/foot/foot.ini ]]; then
  sed -i -E "s/^font=[^:]*(:size=[0-9.]+)?/font=$font_name\1/" ~/.config/foot/foot.ini
fi
```