v0.2.2 - Quality Release

rlvgl v0.2.2 Release Notes

v0.2.2 is a quality release: it makes the crates.io distribution
actually work and adds the CI to keep it that way. (v0.2.1 published
with a broken simulator feature and is superseded.)

Short Release Summary

Fixes every known packaging defect in the published crate set and
introduces the CRATES-CI initiative (docs/crates-ci/): pre-publish
and post-publish gates that build the creator GUI and a user-authored
simulator from packaged crates, plus a headless test harness for both
headed surfaces.

Fixed — crates.io consumers

• rlvgl --features simulator now builds from crates.io
  (rlvgl-app-disco-demo icons were referenced outside the crate root
  and could never be packaged; vendored in).
• rlvgl-platform now builds on macOS hosts (ELF link_section in the
  blit scratch buffer is gated to bare-metal targets).
• rlvgl-audio-meters-core added to the publish order (was
  publish = true and depended on by rlvgl-widgets, but never
  published on change); the publish-order test now derives the
  crate set from cargo metadata so omissions fail CI.
• Packaging metadata, include sets, and feature-resolution-order fixes
  from the v0.2.1 cycle (fontdue in rlvgl-core, disco-assets
  metadata, publish-order dev-dependencies).

New — testing & CI (CRATES-CI-00…05)

• Gate P (crates-ci.yml): every PR and release branch packages all
  25 publishable crates in publish order and builds three consumer
  projects against the packaged set — a library consumer, the
  rlvgl-creator CLI (the cargo install shape), and a user-authored
  simulator per docs/CUSTOM-SIMULATOR.md. Publishing requires Gate P
  green.
• Gate R (gate-r.yml): the same consumers against real crates.io,
  after every publish and daily.
• Creator GUI testing: egui_kittest in-process harness with
  snapshot baseline (Layer K), and a new
  rlvgl-creator --automation-headless --playit-port=<n> mode
  (creator_ui_automation feature) serving the playit wire protocol
  over TCP (Layer W) — the same playit/node client now drives
  disco-sim, user simulators, and the creator GUI, all without a
  display server.

Docs

• docs/crates-ci/CRATES-CI-00-CONCEPTS.md — ratified concepts doc for
  the initiative.
• no_std STM32H747I-DISCO provenance notes.