/**
 * buildTaskTree — pure-functional task hierarchy builder.
 *
 * Accepts a flat array of tasks and constructs a tree of {@link TaskTreeNode}
 * objects. No I/O, no DB access — all input supplied by the caller.
 *
 * @arch SDK Tool (Category B) — pure, no side effects, contracts-typed
 * @task T10068
 * @epic T9835
 */
import type { BuildTaskTreeInput, BuildTaskTreeOptions, BuildTaskTreeResult } from '@cleocode/contracts';
/**
 * Build a task hierarchy tree from a flat array of tasks.
 *
 * Pure functional — no I/O. The caller is responsible for loading tasks and
 * passing them in. When `rootId` is provided, only the subtree rooted at that
 * task is returned. When `opts.withBlockers` is true, each node is annotated
 * with `blockerChain` and `leafBlockers`.
 *
 * @param tasks - Flat array of all tasks (or a pre-filtered subset)
 * @param rootId - Optional root task ID; returns full tree when omitted
 * @param opts - Tree-build options
 * @returns Tree nodes and total node count
 *
 * @example
 * ```typescript
 * const { tree, totalNodes } = buildTaskTree(allTasks, 'T042');
 * console.log(`${totalNodes} nodes in subtree`);
 * ```
 *
 * @example
 * ```typescript
 * const { tree } = buildTaskTree(allTasks, undefined, { withBlockers: true });
 * console.log(tree[0].blockerChain);
 * ```
 */
export declare function buildTaskTree(tasks: BuildTaskTreeInput[], rootId?: string, opts?: BuildTaskTreeOptions): BuildTaskTreeResult;
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