TerminalFont (Ghostty): fix font-family fallback order

[njkdev]

Summary

Ghostty treats repeated font-family as an ordered fallback list. The first entry is the primary, later entries are fallbacks for codepoints the primary lacks (docs). parseGhosttyConfig had this reversed: each entry overwrote the primary and demoted the previous one, so the last entry was reported as the terminal font.

Regression: 2.53.0–2.63.1 were correct (!fontName.length ? &fontName : &fontNameFallback, from #1972 for #1967). 2.64.0 rewrote the block to last-wins; #2448 carried that into the static parser.

Also handles font-family = "", which Ghostty documents as resetting the list.

Reproduction

Config:

font-family = TX-02-Variable
font-family = Menlo
font-family = Monaco
font-size = 14

Before: Terminal Font: Monaco (14pt) / Menlo
After: Terminal Font: TX-02-Variable (14pt) / Menlo

The primary font wasn't reordered, it was dropped. ghostty +show-config confirms the config order.

Only one fallback slot exists, so Monaco is still dropped. This is unchanged by this PR.

Testing

macOS 27.0, Ghostty 1.3.1, built from dev. Verified multiple entries, "" reset, and single-entry configs. Not tested on Linux or Windows; the change is in platform-independent parsing code.

Checklist

• I have tested my changes locally.