v0.2.0

First packaged release with prebuilt binaries for all platforms, including
aarch64 Linux for single-board computers (Raspberry Pi 4B/5, Orange Pi 5
Plus/5 Max).

Added

• Headless orcarein run "<task>" — execute one task non-interactively and
  exit (scriptable / CI-friendly).
• orcarein issue <number> — fetch a GitHub issue and work it end-to-end
  (bring-your-own-key self-bootstrap loop).
• Cost/usage meter: per-turn token + cache-hit + spend line, context-window
  fill %, an economy cache mode, and /usage (= /context) on demand.
• Tool-call repair: malformed tool calls are corrected and surfaced as
  self-correcting errors instead of aborting the turn.
• Session management: interactive session resume picker, session delete,
  and unambiguous short-id prefix matching for resume/delete.
• Terminal UX: an alt-screen overlay + pager for /show <file> and /history,
  with / incremental search (n/N navigation, wrap-around, match highlighting);
  a GPIO live monitor (orcarein hw monitor, hardware feature). All
  capability-gated — degrades to plain output over SSH / serial / headless.
• Cross-SoC hardware layer (orcarein-hardware): board GPIO profiles for
  Raspberry Pi 4B/5 and Orange Pi 5 Plus/5 Max (pinouts transcribed from the
  official vendor docs), and a gpiocdev-based GPIO backend that sets/reads
  pins by logical name across Broadcom and Rockchip boards.

Changed

• HTTP client now uses rustls instead of OpenSSL — portable
  cross-compilation to aarch64 and bundled roots (no system cert store needed
  on minimal SBC images).
• CI now lints and MSRV-checks the full feature matrix
  (default / --all-features / --no-default-features).
• Hardware GPIO backend migrated from the retired, Broadcom-only rppal to the
  SoC-agnostic Linux character device (gpiocdev).