RFE JavaScript: add a configurable Dark Reader opt-out to preserve application appearance

[jsfan3]

Motivation

Dark Reader is widely used: the Chrome Web Store lists 7 million users, and Mozilla Add-ons lists over 1.3 million Firefox users (figures checked on 26 September 2026).

I use Dark Reader and want the JavaScript port to preserve the app's own colors and legibility when the extension is active, preventing unwanted changes and rendering anomalies. This matters even for an app with one fixed palette, such as a light-only theme; it should not require a dark theme or a theme selector.

Dynamic is Dark Reader's default mode and already supports a documented website opt-out.

Proposed behavior

Please include Dark Reader's supported opt-out in the generated index.html head, present from the initial HTML response:

<meta name="darkreader-lock">

Dark Reader documents this mechanism.

Add a new proposed build hint, for example javascript.darkreaderLock:

• true (proposed default): include the meta tag.
• false: omit the tag, leaving Dark Reader to follow its normal settings.

The default opt-out should apply to every app, including apps with a single theme. For apps that support theme changes, it should preserve their existing handling of system preferences and manual theme choices.

Expected behavior and coverage

With the opt-out enabled, Dark Reader's Dynamic mode should preserve the app's own text, backgrounds, dialogs and input fields, including in a light-only app.

Dark Reader currently checks the lock in its Dynamic implementation. Its Filter, Filter+ and Static paths do not check the tag, and neither does the early fallback stylesheet. Extending the lock to those paths requires a Dark Reader change. Please document this coverage when exposing the CN1 hint.

[shai-almog]

This is the same as: #5913