fix reconcile loop: remove invalid Future.wait(), use sleep loop
Io.Future(void).wait() doesn't exist — futures use .await(io) and
are not threadsafe across fibers. replace startup_future.wait() with
a simple initial sleep (the first reconciliation pass runs 5 min
after startup anyway, well after spawnWorkers finishes).
also use 1-second sleep increments for shutdown responsiveness,
matching the subscriber backoff pattern.
caught by `zig build` (exe target) — `zig build test` misses this
due to lazy analysis when no test references the code path.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>