runnerd v0.1.0

First public release of runnerd. This release provides the complete planned
scope for a local, single-user Linux task runner.

Added

• runnerd daemon and runnerctl client communicating over a permission-bound
  Unix Domain Socket.
• Length-prefixed binary framing with PING, SUBMIT, STATUS, LIST, and CANCEL
  operations.
• Single-threaded epoll event loop for client connections, child output
  pipes, signalfd notifications, and timerfd deadlines.
• Process execution through fork/execve, with an exec error pipe that
  distinguishes startup failure from a program exiting with code 127.
• Per-job process groups for supervising the direct child and its descendants.
• FIFO scheduling with a configurable --max-running concurrency bound.
• Cancellation and execution timeouts with SIGTERM followed by SIGKILL
  after a one-second grace period.
• Persistent stdout/stderr files with private permissions and a 10 MiB limit
  per stream; excess output is drained and discarded to prevent pipe stalls.
• In-memory job states and result queries, including exit codes, exit signals,
  output byte counts, and truncation flags.
• 84 GoogleTest unit and integration tests covering protocol handling,
  scheduling, process lifecycle, cancellation, timeouts, and output capture.
• GitHub Actions checks for GCC Debug, Clang Debug, GCC Release, ASan, and UBSan.
• A reproducible end-to-end latency benchmark reporting throughput and
  P50/P95/P99/Max latency.

Known limitations

• Linux-only and intended for trusted users and workloads on one host.
• Job metadata and JobId allocation are not persisted across daemon restarts.
• Persisted output cannot yet be retrieved through runnerctl.
• No authentication, sandboxing, cgroup isolation, or remote execution.
• The protocol and command-line interface may still change during the 0.x
  release series.