[FEATURE] Desktop app: let the font settings use any installed font (e.g. Consolas Nerd Font)

Request

Claude Desktop's font settings only offer a fixed set of presets (Sans Serif, OpenDyslexic, …). Please add a custom option that accepts any font installed on the system, such as Consolas Nerd Font, for:

• chat / message text
• interface chrome (sidebar, menus, buttons)
• monospace text: code blocks, tool output, diffs, and the prompt input in the Code tab

Why

I run claude in a terminal set to Consolas Nerd Font. The Desktop Code tab is the only place my sessions don't render in it, and I can't fix that myself. If the monospace font could be set to a Nerd Font, this would probably also fix the missing-glyph boxes reported in #89839 and #70301.

Mods don't cover this

Mods (v2.1.287+) can redraw parts of the Code tab, but the Text element only takes color, backgroundColor, bold, italic, underline, dimColor, inverse and wrap. There's no font-family prop and no CSS hook, and the prompt input isn't a render site. This needs a built-in setting.

Suggested shape

Under Settings → Appearance, add a "Custom…" choice to each font picker that takes a font-family name or lists installed fonts. Keep the current presets.

Related: #94208 (font size), #50543 (font size without scaling the UI), #97928 (interface font not applying).

Environment

Claude Desktop 2.16120.0, macOS (Darwin 25.5.0), Code tab.