fix(copilot): respect widget theme for logo URL

[axelray-dev]

Summary

In the Copilot widget, the logo URL was following the OS color scheme instead of the widget theme (mount config or vite-ui-theme in localStorage).

Root cause: Header renders the shared frontend Logo, which reads the frontend ThemeProvider context. That provider is not mounted in the copilot tree, so the logo fell back to system / prefers-color-scheme.

Changes

• Add optional themeVariant prop on frontend/src/components/Logo.tsx. When set, it is used for getLogoEndpoint; otherwise existing useTheme() behavior is unchanged for the main app.
• Pass copilot useTheme().variant from libs/copilot/src/components/Header.tsx into Logo.
• Add a Vitest regression that forces themeVariant="light" and asserts the logo endpoint is called with light.

Verification

• pnpm Vitest for frontend/tests/Logo.spec.tsx
• Frontend typecheck
• Copilot production build
• ESLint and Prettier on touched files

Fixes #2976

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Summary by cubic

Fixes the Copilot widget logo so it follows the widget theme (mount config or vite-ui-theme) instead of the OS color scheme, ensuring the correct light/dark logo URL.

• Bug Fixes
  • Added optional themeVariant prop on Logo; default behavior unchanged.
  • In Copilot Header, pass useTheme().variant into Logo so getLogoEndpoint uses the widget theme.
  • Added a Vitest test: themeVariant="light" triggers getLogoEndpoint('light', ...).

^{Written for commit 41e7fd2. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 3 files

_{Re-trigger cubic}

[dokterbob]

@codex review