[FEATURE]: add catppuccin-latte as a standalone theme

Feature hasn't been suggested before.

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Describe the enhancement you want to request

Current Problem

Catppuccin has four official flavors to make themes: latte, frappe, macchiato, and mocha. OpenCode currently ships three as named themes: catppuccin (mocha), catppuccin-frappe, catppuccin-macchiato, but latte, the only light one, has no standalone entry. It only exists as the light variant of catppuccin, so there's no way to select it by name; the only path is switching the theme mode to light.

It seems fine to keep latte only as catppuccin's light variant, but that makes it undiscoverable and inconsistent with the other three flavors each having a named entry.

Proposed Solution

Add catppuccin-latte as a built-in theme, following the same one-flavor-per-theme pattern as catppuccin-frappe and catppuccin-macchiato. It would render the latte palette in both light and dark mode, independent of the mode toggle. Purely additive — the existing catppuccin theme keeps its current behavior.

Additional Context

I am happy to implement this issue if it is approved.