[FEATURE]: Generate and passthru schema for both `config.json` and `tui.json`

[delafthi]

Feature hasn't been suggested before.

• I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement you want to request

Since https://github.com/anomalyco/opencode/releases/tag/v1.2.15 TUI configuration is in a separate file (tui.json) with a separate schema. The current nix package declaration still only generates and exports only the schema for config.json.