[FEATURE] /insights report: dark-mode support (prefers-color-scheme)

Description

The HTML report generated by /insights is light-only: zero prefers-color-scheme handling and a hardcoded light palette. On a system in dark appearance, opening the report is a full-brightness white page.

Previously requested in #27187, which was closed as stale without implementation.

Environment

• Claude Code 2.1.176
• macOS (darwin), report opened in Chrome

Suggested fix

A real dark theme would be ideal, but even a minimal smart-invert override works well as a stopgap — I patch my local reports with:

@media (prefers-color-scheme: dark) {
  html { filter: invert(0.92) hue-rotate(180deg); background: #111; }
  img, video { filter: invert(1) hue-rotate(180deg); }
}

This keeps the brand hues roughly intact while flipping the background dark, and only activates when the OS is in dark mode.

🤖 Filed with Claude Code on the user's behalf