feat(tui): detect terminal color scheme and apply light-optimised palette

Squash of the linearized fix/tui-color-scheme-v2 merge and the follow-up
catalog regeneration. Renders error cause chains at every diagnostic seam
(origin/fetch-failed-diagnostics) and adds color scheme detection with a
light-terminal palette.

eslint.config.mjs

@@ -14,6 +14,7 @@ export default tseslint.config(
       '**/.doc-typecheck-*/**',
       'website/.generated/**',
       'vendor/**', // vendored source keeps upstream style and idioms
+      'native/**', // imported landlock-run subtree: self-contained workspace with its own gates (native/README.md)
       '**/*.js',
       '**/*.mjs',
       '*.config.ts', // root tool configs (vitest, tsdown) — no project service