v0.3.0

v0.3.0 - 2026-06-16

Marionette's third release makes deterministic std.Io execution the primary
integration tier:

• Adds scheduler-backed Io.async, Io.concurrent, and Io.await, including
  task-side suspension and main-context scheduler driving.
• Routes simulated sleep and disk-operation latency through scheduler
  deadlines, so a long I/O operation cannot skip an earlier timer.
• Adds traced deterministic Io.random / Io.randomSecure and compares replay
  outcomes symmetrically, including failures.
• Runs the pinned g41797/mailbox validation and the bounded-queue capability
  validation entirely through ordinary std.Io tasks.
• Adds an external-style fixed-frame KV client/server written only against
  std.Io.net, with deterministic happy-path replay and a
  partition/timeout/heal retry scenario.
• Adds zig build validate-std-io-net-kv plus runnable correct and planted-bug
  scenarios. The exact oracle catches duplicate mutation application even when
  the final value is unchanged.
• Suspends std.Io.net accept and read operations cooperatively and models
  stream latency, send-time loss, delivery-time partitions, healing, retry
  timeouts, and graceful close.
• Models disk crashes as process restarts for the file layer: open handles are
  invalidated and cached lengths are refreshed from durable disk state.
• Fixes Zig 0.16 fiber context-switch constraints and optimizer visibility,
  adds unwind-safe entry stacks, eagerly reclaims completed fiber stacks, and
  adds POSIX guard pages with a portable stack-canary fallback.
• Splits disk, network, and std.Io internals into focused modules and narrows
  obsolete top-level API aliases.
• Makes failed simulation construction roll back teardown registrations,
  enforces one simulation per world, and shares rooted logical-path validation
  between simulated and production disks.
• Makes production directory sync fail explicitly with
  error.DirectorySyncUnsupported rather than reporting durability without
  performing it.
• Disables x86_64 Windows fiber execution until the Win64 entry trampoline has
  execution coverage; the disabled target remains compile-checked.
• Expands CI to Debug, ReleaseSafe, and ReleaseFast validation, macOS execution,
  a Win64 fiber compile check, and bounded job timeouts.

Known limits remain: fibers are cooperative rather than preemptive; one world
hosts one simulation; current std.Io.net listener/connection allocation
consumes fixed topology nodes; Io.Group, cooperative cancellation, logical
process restart, cross-process production networking, and complete host
filename parity remain roadmap work.