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0064: Themes can dress the core Heinzelmännchen with a palette and snow

Context and Problem Statement

The maintainer wants a wintry Heinzelmännchen supplied by a theme, with snow on its cap and a frosty scarf. The original drawing already composes age, beard, hat, shirt, build and accessories from typed shapes. Arbitrary SVG icon sets are a larger extension; this first slice needs only checked colours and a closed decoration vocabulary.

Considered Options

  • A checked [heinzel] theme table, applied to the existing drawing (chosen).
  • Arbitrary icon files: defer to the broader theme-icon-set design; file validation and fallbacks need their own implementation, and a fixed icon would lose the person's five look choices.

Decision Outcome

Chosen option: a checked [heinzel] theme table, because themes can decorate the drawing while age, beard, build, state and accessories keep working.

  • Theme.heinzel is optional. Its palette permits only hat, shirt and scarf, each a checked hex colour, and decorations permits only snow, at most once. Unknown keys, CSS and markup are refused.
  • Palette colours replace defaults only. A person's explicit hat or shirt colour still wins.
  • Snow adds a patch on the cap (none for a baby), static snow dots and a scarf; a scarf already requested is never duplicated. It applies to every age, build and state in full, bust and head views.
  • Theme changes update mounted avatars; choosing a theme without the table returns to the core drawing.
  • No new code, network request, asset route or CSP exception comes from a theme. The plain TypeScript renderer remains usable by the icon generator with no theme, producing the same default icons.
  • The CLI and MCP theme listing expose the same palette and decorations through the theme model.

Consequences

  • Good: a theme can make a snowy crew without replacing personal look choices.
  • Bad: the palette covers three parts, and snow is the only decoration. More parts or full icon sets require an explicit extension rather than free-form graphics.

Confirmation

Kernel theme tests refuse unknown keys, invalid colours and decorations. Avatar tests cover every age and build, explicit colour precedence, scarf deduplication and returning to the undecorated drawing. Theme-service integration checks the table reaches CLI JSON. The generated OpenAPI schema describes the same model.