v0.13.0

Added

• Built-in async DNS resolver on Linux (io_uring backend), replacing getaddrinfo. Reads /etc/hosts
  and resolv.conf, supports search domains, CNAME following, parallel A/AAAA queries, EDNS0,
  TCP fallback for large responses, response caching, and deduplication of concurrent identical
  lookups. Enabled by default on io_uring; opt-in via RuntimeOptions.dns.custom_resolver.
• Runtime.initStatic for stack-allocated or externally-owned Runtime instances that don't
  need a heap allocation.
• Single-threaded build support (single_threaded = true).

Changed

• BREAKING: DNS lookup API changed from an iterator (Result with next() / deinit()) to a
  caller-supplied buffer (lookup(&storage, options) returning a count). Eliminates the allocation
  and the need to remember deinit.
• BREAKING: BroadcastChannel.subscribe() now returns a Consumer value instead of taking a
  pointer, and unsubscribe() is gone — consumers no longer need to be unregistered.
• HostName now accepts numeric IPv4 and IPv6 addresses in addition to DNS names.
• io_uring: when the submission queue is full, operations are queued internally and retried on the
  next loop iteration instead of failing the caller.
• Coroutine stacks are now periodically evicted from the pool when they exceed max_age, reclaiming
  virtual memory that would otherwise accumulate during idle periods.