/**
 * Small, side-effect-free input-validation helpers shared by the cli-core library API. Each returns a
 * discriminated union so call sites pattern-match without throwing across the public boundary
 * (matches the three CLIs' `lib/validation.ts`). The project-path resolution ladder here backs the
 * T5 `install-plugin` policy (design 02 §T5): resolve `path? → --path? → cwd`, then marker-probe.
 */
/** A validated, absolute path result. */
export type ValidatedPath = {
    ok: true;
    projectPath: string;
} | {
    ok: false;
    error: Error;
};
/** Require a non-empty string and resolve it to an absolute path. */
export declare function requireProjectPath(raw: unknown): ValidatedPath;
/** Require a non-empty path that also exists on disk (does not need to host an engine project). */
export declare function requireExistingPath(raw: unknown): ValidatedPath;
/**
 * Resolve the T5 project-path ladder — an explicit positional arg, then a `--path` flag, then the
 * current working directory — and resolve the winner to an absolute path. The `--path`/`cwd` fallback
 * is exactly what closes defect B1 (unity `install-plugin` used to demand an explicit path).
 * `cwd` is injectable for deterministic tests. Never throws.
 */
export declare function resolveProjectPathLadder(opts: {
    positional?: string;
    path?: string;
    cwd?: string;
}): {
    source: "positional" | "path" | "cwd";
    projectPath: string;
};
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