/**
 * Expand user-shorthand prefixes in a path string. Currently:
 *
 * - `~` alone → `$HOME`
 * - `~/foo` (or `~\foo` on Windows) → `$HOME/foo`
 * - `~user/...` throws (POSIX-only; the platform complexity isn't
 *   worth the small payoff — also lets people write a literal
 *   `~user-typed-name` dir at the project root by quoting `./~user...`).
 * - everything else returns unchanged.
 *
 * This is the single owner of path-shorthand policy for the stdlib.
 * Future rules (env-var expansion, NFC normalization, etc.) land
 * here, not at call sites. Anything in `lib/stdlib/` that resolves a
 * user-typed path string goes through `contained.ts` (`root`,
 * `resolveUnder`, `wholePath`) or `resolveDir`, which call this helper
 * first. Do not re-implement the policy locally.
 *
 * Layering: `expandPath` is a pure string transform with no async and
 * no base-directory awareness; the home directory is `homeDir`, which a
 * caller takes from `host.system.homeDir()`. Resolving against the cwd
 * and refusing symlinks live one layer up, in the file part of the host.
 * Keeping the layers split means `expandPath` is testable in isolation.
 *
 * Does NOT resolve to an absolute path. Callers pass the result to
 * `root`, `wholePath`, or `resolveDir`.
 *
 * `expandPath("")` returns `""` unchanged so empty-string sentinels
 * pass through (callers that disallow empty dir handle that
 * themselves with a clearer error).
 */
export declare function expandPath(p: string, homeDir: string): string;