feat: add Prelude themes for Process Compose

[cooper (czxtm)]

Summary

• Inspected Stackpanel's actual Process Compose input: github:Platonic-Systems/process-compose-flake, pinned in flake.lock to 464ff6880737f063c3f0d3d2c7781fda9190868f.
• Confirmed that process-compose-flake exposes flakeModule, lib, and a template; its module exposes process settings and CLI wrapper options, but no Process Compose theme-definition hook (theme, themes, style attrsets, or custom-theme file option).
• Source Prelude palettes from the pinned Prelude flake (inputs.prelude.lib.themes) and map those Nix theme definitions into Process Compose's supported custom theme.yaml schema.
• Added stackpanel.process-compose.theme to select a Process Compose theme, defaulting to the active Prelude theme or minted.
• Generate .stack/gen/process-compose/theme.yaml and launch Process Compose with --theme "Custom Style" via the existing dev wrapper.
• Documented the Process Compose theme selection path.

Approach

process-compose-flake does not expose a first-class theme mechanism. Because upstream Process Compose itself loads custom TUI themes from a config directory (theme.yaml) and activates them as Custom Style, Stackpanel now uses Prelude's Nix theme attrset as the source of truth and renders only the required Process Compose custom theme file. This avoids hand-copying Prelude colors while still using the only theme mechanism Process Compose provides.

Ported themes

Sourced from inputs.prelude.lib.themes:

• phosphor
• minted
• amber
• solarized
• nord
• gruvbox
• mono
• apathy
• paper
• prelude

Config paths and selection

• Nix role mapping: nix/stackpanel/modules/process-compose/themes.nix
• Generated Process Compose theme file: .stack/gen/process-compose/theme.yaml
• Select a theme explicitly:

  stackpanel.process-compose.theme = "nord";

• If unset, Process Compose follows stackpanel.prelude.theme; if that is unset, it falls back to minted.

Verification

• git diff --check and git diff --cached --check passed.
• Full repo gates were not run because this cloud image does not have nix, bun, nixfmt, alejandra, or bd available on PATH.

  

[github-actions]

Preview pr-68 has been destroyed.

[github-actions]

Docs preview pr-68 has been destroyed.

[linear-code]

ENG-945