/**
 * Single source of truth for the plan/lessons filename timestamp format, shared
 * by the generator (`GitHubSourcePlanService.writeGeneratedPlan`) and the parser
 * (`GroupLaunchService`) so the two can never drift.
 *
 * The time separator switched from `:` to `-` to produce Windows-safe filenames
 * (a `:` is an invalid path character on Windows and breaks `actions/checkout`
 * on `windows-latest`). The parser accepts BOTH forms so already-committed
 * colon-named plans keep resolving; no migration is performed.
 */
/**
 * Format `now` as a plan-filename timestamp in local time.
 *
 * - `windowsSafe` (default): `YYYY-MM-DD-HH-MM` — no colon.
 * - legacy: `YYYY-MM-DD-HH:MM` — restored when `defaults.windowsSafeNames` is off.
 */
export declare function formatPlanTimestamp(now: Date, windowsSafe?: boolean): string;
/** Build `<timestamp>-<slug>.md` for the given `now`, slug, and separator mode. */
export declare function buildPlanFileName(now: Date, slug: string, windowsSafe?: boolean): string;
/**
 * Match a plan filename's leading `YYYY-MM-DD-HH-MM` / `YYYY-MM-DD-HH:MM`
 * timestamp (either separator in the HH/MM position) and return the captured
 * prefix, or `null` when absent.
 *
 * The captured prefix stays lexicographically sortable: both `:` (U+003A) and
 * `-` (U+002D) sort after the digits that precede them, so cross-form ordering
 * within the same minute is irrelevant and same-minute ties fall back to mtime
 * at the call site.
 */
export declare function parsePlanTimestampPrefix(filename: string): string | null;
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