v0.6.0

[0.6.0] - 2026-10-19

Added

• Real-process reliability tests for SolidEngine (worker SIGKILL, lost ACK, server
  restart, clean stop); Backends::Worker now survives connection errors while
  settling a job and lets the lease expire for redelivery.
• Backend adapters: Backends::Base contract, Backends::Redis and
  Backends::SolidEngine; config.backends, config.channel_backends and
  per-channel routing in Publisher and Conductor.
• config.execution_mode (:ractor default, or :thread): non-Redis backend
  workers run in Ractors, each with its own client, so the backend no longer
  determines CPU parallelism. Ruby 4 is recommended: on 3.4.4 Ractor CPU cost per
  job rises sharply beyond 4 workers.