The generated C now builds as an ESP-IDF component for the ESP32 (Xtensa
LX6), and a new CI job builds four programs into firmware and boots them in
Espressif's QEMU, checking their console output.

- codegen: under ESP_PLATFORM, emit an app_main() that calls main() (ESP-IDF
  starts firmware there), and leave out the termios raw-mode helpers (ESP-IDF
  compiles its termios out unless VFS termios is configured).
- runtime: MAX_CORES, MAX_ACTORS_PER_CORE, SCHEDULER_DRAIN_BATCH and
  QUEUE_SIZE are overridable with -D. At the defaults the cooperative
  scheduler's static tables are ~10 MB (16 Schedulers of ~650 KB, one used);
  an ESP32 has ~320 KB of DRAM. Defaults unchanged.
- tests/esp32: an ESP-IDF project template (cooperative scheduler, the
  ci-wasm runtime file list, small tables) and a driver that runs the
  official espressif/idf:v6.1 image with podman or docker. hello, counter,
  test_coop_chain and test_platform_caps all pass, at ~150 KB of firmware.
- make ci-esp32, and a ci-esp32 job in ci.yml.

Without the app_main forwarder all four builds fail to link; without the
termios guard or the smaller tables the spike did not compile or link.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

chore: release 0.790.0

Run Aether on the ESP32 under emulation (ci-esp32)

chore: release 0.791.0