Feature: expose terminal line height as a term:lineheight setting

[johnhreardoniv]

Summary

Wave exposes term:fontsize and term:fontfamily, but there is currently no way to adjust terminal line height / line spacing. Increasing the font size is the only vertical-spacing lever today, and it enlarges the glyphs too. Please expose xterm.js's lineHeight option as a term:lineheight config key.

Motivation

• Terminals like WezTerm, kitty, and iTerm2 all offer a line-height multiplier; it's a common readability knob.
• With serif / slab-serif monospace fonts (e.g. Monaspace Xenon, Courier Prime), the default leading can feel cramped. A ~1.1–1.3 multiplier dramatically improves readability without enlarging the characters.
• xterm.js already supports ITerminalOptions.lineHeight (a multiplier of the cell height), so this should be a thin pass-through rather than new rendering work.

Proposed

• Add term:lineheight (float, default 1.0) alongside the existing term:* settings, plumbed straight to the xterm.js lineHeight option.
• Ideally also honor it as block metadata so an individual terminal block can override the global value (useful for status/monitor blocks vs. working terminals).

Related

• Customise font settings #83 "Customise font settings" (closed) touched font customization generally but not line height specifically.

Thanks — the config surface is otherwise excellent; this is the main typographic-comfort gap versus other terminals.