Adds a Zed theme generated from the canonical palette in the root
README, alongside the existing wezterm and zellij configurations.
The 16 terminal colors carry over unchanged from wezterm/config.lua.
Syntax highlighting follows the spec's stated preference order (blue,
cyan, green) with the Dawn accents reserved for semantic signals and
the rare token roles.
Zed addresses UI surfaces the 16-color terminal palette does not
define. Two neutrals are derived for chrome (#2a2e39, L19) and
elevated surfaces (#313440, L22), both interpolated in CIELAB along
the palette's own neutral ramp so they sit on the ramp the spec
defines. ANSI dim variants are mixed 45% toward the background in LAB
to preserve hue. Overlays use an alpha channel over palette colors
rather than new opaque values.
The theme is generated by build-theme.py, which validates output
against the live Zed theme schema (v0.2.0) and fails if any of its
142 style keys is missing.
