/**
 * One-time, non-destructive migration from the old project-local data location
 * (`{project}/token-optimizer/`) to the platform-global one.
 *
 * Deliberately COPIES rather than moves. A move of a live SQLite file across a
 * plugin upgrade is how trends history gets lost for real; leaving the original
 * in place means a bad migration is recoverable by pointing
 * TOKEN_OPTIMIZER_DATA_DIR back at the project.
 *
 * Never throws. A migration failure must not take the plugin down with it: the
 * worst acceptable outcome is starting fresh with a warning, not a crash.
 *
 * @param projectSlug Session DBs MUST land in the same per-project subdirectory
 *   the readers scan (`sessions/{slug}/`). Legacy data was project-local, so it
 *   unambiguously belongs to this project's slug. Writing it flat would copy the
 *   files somewhere no reader ever looks, which is data loss wearing a success
 *   message.
 * @returns true when files were copied on this call, false otherwise.
 */
export declare function migrateLegacyDataDir(projectDir: string, targetRoot: string, projectSlug: string): boolean;
//# sourceMappingURL=migrate.d.ts.map