// Written by the mesh (module betterbird, novox/hq issue 345, issue 586): the preferences the module manages at
// Betterbird's own default. It holds no value of the operator's: the operator's setup is the module's setting
// prefs, mesh-wide with a node's own layer over it, which the tools place in the profile's user.js, where it wins
// at every start; the policy's locks (distribution/policies.json) win over everything. betterbird_config shows the
// layers and the drift. Change it in the catalogue, never here.
//
// A line "keeps Betterbird's default" names a preference the module manages without writing a value: Betterbird's
// own default holds there, and a value the profile saved is drift, which betterbird_config_apply clears.

// keeps Betterbird's default: extensions.activeThemeID
// The default theme (default-theme@mozilla.org) follows the desktop's dark mode. Betterbird keeps the active theme
// in its add-on database, so another theme is changed back in the add-on manager, never by clearing prefs.js.
// keeps Betterbird's default: browser.display.use_system_colors
// Betterbird's own colours, which the default theme is drawn for.
// keeps Betterbird's default: layout.css.always_underline_links
// Links are underlined only where the message's own style says so.
// keeps Betterbird's default: mail.spam.manualMark
// Marking a message as junk by hand does nothing more than mark it.
// keeps Betterbird's default: mail.compose.show_attachment_pane
// The composer shows its attachment pane only when a message has attachments.