/* system — follows OS preference; active when no data-theme attribute is set */
@media (prefers-color-scheme: dark) {
    :root:not([data-theme]) {
        color-scheme: dark;
        --bg: #0d1117;
        --panel: #161b22;
        --text: #e6edf3;
        --muted: #8b949e;
        --line: #30363d;
        --accent: #58a6ff;
        --accent-strong: #388bfd;
        --danger: #f85149;
        --success: #3fb950;
        --shadow: 0 12px 28px rgba(0, 0, 0, 0.4);
    }

    :root:not([data-theme]) input,
    :root:not([data-theme]) textarea {
        background: var(--panel);
        color: var(--text);
        border-color: var(--line);
    }

    :root:not([data-theme]) .sidebar {
        background: color-mix(in srgb, var(--bg) 80%, #000 20%);
    }
}