#163 Fix dark inline code styling

Summary

• add dark-mode inline code colors so code snippets are readable on dark docs pages
• keep full code block contents transparent so they inherit the code block theme
• add CSS regression coverage for dark inline code readability

Tests

• node --test scripts/*.test.mjs
• node scripts/sweep-artifacts.mjs --check

Verification

• Checked the local Mintlify preview on /ai/connecting-ai-tools in dark mode; the MCP URL now renders with light text on a dark gray surface.

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Summary by cubic

Fixes dark-mode inline code styling so inline snippets are readable on dark docs pages. Keeps code block backgrounds transparent to inherit the theme and adds a CSS test to prevent regressions.