/**
 * `ai-usage hook`: Claude Code's UserPromptSubmit hook. Prints a notice when the
 * session's context is at or above the compact limit, and nothing otherwise.
 *
 * It ALWAYS returns 0. For this hook event Claude Code treats exit code 2 as
 * "block the prompt and erase it", so a hook that failed -- on garbage stdin, a
 * missing transcript, or a mistyped flag -- would eat what the user just typed.
 * That is why it reads its two flags itself instead of going through
 * `parseArgs`, which rejects what it does not understand: here an unknown or
 * malformed flag is reported on stderr and otherwise ignored.
 *
 * It runs on every prompt, so it is also the one command that must stay light:
 * `index.ts` dispatches here without loading the rest of the CLI, and it opens no
 * database, syncs nothing and loads no pricing -- it reads the tail of one file.
 */
export declare function runContextHook(argv: string[]): Promise<number>;