/**
 * Pure tree mutations. Every function returns a NEW tree and never mutates its
 * input (clone-on-write). All structural invariants (#1) are funnelled through
 * `normalizeRoot`, which collapses empty tabgroups + single-child splits,
 * cascading upward, while keeping the root a LayoutNode.
 */
import type { LayoutTree, Orientation, SizeConstraint } from './types.js';
export declare function setSizes(t: LayoutTree, splitId: string, sizes: readonly number[]): LayoutTree;
/**
 * Set (or clear) the fixed-px constraint on child `childIndex` of split
 * `splitId`. Pure (clone-on-write). Lazily materializes an all-null constraints
 * array aligned with `children` when absent, then writes the slot. Clearing
 * (`constraint === null`) keeps the array even if all entries become null.
 */
export declare function setConstraint(t: LayoutTree, splitId: string, childIndex: number, constraint: SizeConstraint | null): LayoutTree;
export declare function setActive(t: LayoutTree, groupId: string, panelId: string): LayoutTree;
export declare function closePanel(t: LayoutTree, panelId: string): LayoutTree;
export declare function extractPanel(t: LayoutTree, panelId: string): {
    tree: LayoutTree;
    extracted: string;
};
export declare function insertPanel(t: LayoutTree, panelId: string, dest: {
    groupId: string;
    index?: number;
}): LayoutTree;
export declare function movePanel(t: LayoutTree, panelId: string, dest: {
    groupId: string;
    index?: number;
}): LayoutTree;
export declare function splitPanel(t: LayoutTree, atPanelId: string, dir: Orientation, newPanelId: string, side: 'before' | 'after'): LayoutTree;
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