/**
 * Tone math (guuey#403 §2) — the two-panel tone pair, its perceptibility
 * floor, and the chat-palette derivation.
 *
 * The floor is CALIBRATED, not invented (ggui#633's scars): the console's
 * first cut at ΔL* 3.5 measured below perception; their shipped pair
 * (#F4F3ED warm paper vs #E4E4E2 neutral chrome) reads clearly at ΔL* 5.2
 * because the warm→neutral TEMPERATURE step does perceptual work lightness
 * alone doesn't. Hence the OR-form floor:
 *
 *     ΔL* ≥ 6  —  OR  —  a hue-temperature step (Δab ≥ 2) with ΔL* ≥ 5
 *
 * Both arms reject the failed 3.5 cut; the strict arm alone would have
 * rejected the founder-certified shipped pair. The platform's theme-doc
 * gate applies its own mirror of this rule server-side; this module is the
 * lib's own honesty (derived defaults satisfy the floor BY CONSTRUCTION —
 * pairs that land under it get the documented nudge apart, never a silent
 * pass). Calibration may RAISE the floor; it does not lower it.
 */
/** A resolved tone pair for one mode: two backgrounds + their foregrounds. */
export interface TonePair {
    /** Upper panel (app menus) background. */
    upper: string;
    /** Foreground on the upper tone. */
    upperOn: string;
    /** Lower panel (agent) background. */
    lower: string;
    /** Foreground on the lower tone. */
    lowerOn: string;
}
/**
 * The lib base defaults — the ggui#633 SHIPPED pair for light, and its
 * temperature-step mirror for dark (warm umber menu vs neutral chrome,
 * ΔL* 6.5 — the strict arm). Founder-certified "two-toned and
 * well-distinguished" in light; the dark pair keeps the identical warm→
 * neutral grammar so a mode flip changes brightness, not the layout's
 * character. Both pairs assert the floor in this package's tests.
 */
export declare const DEFAULT_TONES: Record<"light" | "dark", TonePair>;
/** CIELAB (D65) from a `#rrggbb` hex. Throws on a malformed color. */
export declare function hexToLab(hex: string): {
    L: number;
    a: number;
    b: number;
};
/** The perceptibility deltas between two backgrounds. */
export declare function toneDelta(upper: string, lower: string): {
    dL: number;
    dab: number;
};
/** The OR-form floor (module header). */
export declare function meetsToneFloor(upper: string, lower: string): boolean;
/**
 * Reject-under-floor with the explanatory message (the brandAccent
 * posture): overrides that fail perceptibility throw HERE, at wiring time,
 * never render as an invisible seam.
 */
export declare function assertToneFloor(pair: TonePair): void;
/**
 * Base-tier derivation (§2, platform's pick): tones DERIVE from the chat
 * palette's surface/canvas pair, so an already-themed app gets coherent
 * tones for free — theming chat themes the layout, no second authoring
 * step. `surface` grounds the AGENT (lower) panel — it is the chat's own
 * ground — and `canvas` grounds the MENU (upper) panel. Pairs that land
 * under the floor get the documented nudge: the upper tone walks away from
 * the lower along the lightness axis (toward white below L* 50, toward
 * black above — always INTO the pair's existing contrast direction) until
 * the strict arm passes. Deterministic, bounded, and asserted by tests.
 */
export declare function deriveTones(palette: {
    surface: string;
    canvas: string;
    ink: string;
}): Pick<TonePair, "upper" | "lower"> & {
    nudged: boolean;
};
/** Linear sRGB-space hex mix (`t` toward `target`). Exported for tests. */
export declare function mixHex(base: string, target: string, t: number): string;
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