Make it possible to theme code snippets.

[tikurahul]

• Introduces the 0-tier palette for code.

What & why
Makes it possible to theme code snippets.

How I verified it

• npm run-script build:single and verified the changes to the model, as well as rendering.

Checklist

• Read the relevant parts of CLAUDE.md / docs before changing them
• npm run build:single succeeds (from slides/)
• Ran node scripts/test-sync.ts if I touched slides/src/sync/
• New UI strings added to every catalog in slides/src/i18n/
• Document format changes are additive and backward-compatible
• Did not bump the version or cut a release (maintainers sign releases)

[github-actions]

Build size

main (401cade) → main (b0eb3a9)

app	base	PR	change
bento/slides	678.4 KiB	678.0 KiB	-0.4 KiB (-0.06%)
bento/spaces	271.3 KiB	271.3 KiB	0.0 KiB (0.00%)
bento/dash	424.1 KiB	424.1 KiB	0.0 KiB (0.00%)

Updated: 2026-09-12T00:57:31Z

[nyblnet]

Verified both ways in a built shell, real Chrome:

• With theme.codePalette = { c:'#ff0000', s:'#00ff00', n:'#0000ff', k:'#ff00ff' }, the rendered tokens take exactly those colours — comment rgb(255,0,0), string rgb(0,255,0), number rgb(0,0,255), keyword rgb(255,0,255).
• With no codePalette, every token is byte-identical to today's defaults — #6b7f8f, #c98a3e, #b0688f, #5b8def. So existing decks don't move.

Merges cleanly with main, tsc, build:single, shell gate, test-theme 38/38, test-tokenize and test-codediff all pass. Additive: an older shell ignores the key and paints defaults, which is the right degradation. And theme.chartPalette already exists, so this is the natural sibling — the discussion in #446 was right that the theme is where it belongs.

Three small things, none blocking:

1. doc.theme?.codePalette as any — the type is declared right there in model.ts; reading it as the declared shape costs nothing and keeps the compiler on your side.
2. The palette can't set the base text colour: DEFAULT_CODE_COLORS falls through to 'x' for a token with no scope, and codePalette has no x. If that's deliberate (base text follows el.color), a one-line comment saying so would stop the next reader wondering.
3. The defaults now live in two places — code.ts and the starter deck — with the same eight values. If they ever drift, the starter deck shows one thing and a fresh deck another. Having the starter deck spread the constant (or leaving the starter deck alone and letting it inherit) would keep one source of truth. Your call; declaring it on the starter deck is a nice way to show authors the knob exists.

Ready from the slides side.