Same raw oklch(0.13 0.005 260) background color duplicated across 4 unrelated files with no shared token

[JSONbored]

Context

The literal bg-[oklch(0.13_0.005_260)] (an "always-dark code surface" color) is copy-pasted verbatim in apps/loopover-ui/src/components/site/control-primitives.tsx:123 (DiffBlock), apps/loopover-ui/src/components/site/app-panels/maintainer-panel.tsx:829, and apps/loopover-ui/src/components/site/api/try-it.tsx:253,341. No entry in packages/loopover-ui-kit/src/theme.css currently names this value.

Requirements

• Add a token (e.g. --surface-code / .bg-surface-code utility) in packages/loopover-ui-kit/src/theme.css for this color.
• Replace all 4 call sites with the new utility class.

Deliverables

• New design token added
• 4 call sites migrated

Test Coverage Requirements

99%+ Codecov patch coverage on every changed line and branch, plus a regression test that reproduces the exact gap described above (note: apps/** UI code may fall outside the strict Codecov patch gate — check coverage.include before assuming it's enforced here, and add a before/after screenshot table per this repo's UI-PR convention regardless).

Expected Outcome

The always-dark code-surface color is a named, reusable token instead of a magic constant copy-pasted 4 times.

Links & Resources

apps/loopover-ui/src/components/site/control-primitives.tsx:123, apps/loopover-ui/src/components/site/app-panels/maintainer-panel.tsx:829, apps/loopover-ui/src/components/site/api/try-it.tsx:253,341.

[linear-code]

JSO-4683