/**
 * Write `msg` to fd 2 with the `obsidian-brain debug:` prefix and a
 * monotonic millisecond timestamp (seconds since process start). No-op
 * when `OBSIDIAN_BRAIN_DEBUG` is not exactly `"1"` — explicit-truthy
 * check, NOT JS truthiness, so accidental `OBSIDIAN_BRAIN_DEBUG=`
 * (empty string, falsy) doesn't enable.
 *
 * Failures swallowed: fd 2 might be closed in some embed-host scenarios
 * we haven't anticipated. Debug log silently dropping is preferable to
 * the debug log itself crashing the process.
 */
export declare function debugLog(msg: string): void;
/** Exported so tests can verify the gate without monkey-patching env. */
export declare function isDebugEnabled(): boolean;