Implement first ESP32 QEMU runner for esp32dev post-build crash testing #25

Goal

Implement the first ESP32 QEMU-backed emulator path for crash-oriented post-build testing.

Why

The repo already documents QEMU testing direction for ESP32, and the existing crash decoder understands ESP32-family crash output. The practical first slice is narrow: esp32dev only, with clearly documented image-layout and flash-mode constraints.

Scope

• implement QemuEsp32Runner
• support esp32dev only in the first iteration
• define the required artifact bundle: bootloader, partitions, app binary, or merged image
• codify image layout / flash mode constraints for emulator use
• route emulator output through existing timeout and crash classification logic
• add at least one crash fixture and one success fixture

Explicit non-goals

• ESP32-S3 support in the first iteration
• broad ESP32 family coverage
• pretending QEMU coverage is equivalent to hardware validation

Acceptance criteria

• fbuild test-emu works end-to-end for esp32dev
• crash output is surfaced and classified through existing decoding/monitor logic
• constraints are documented clearly in tests/examples/docs
• unsupported ESP32 variants fail explicitly instead of silently trying to run

References

• lcgamboa/qemu: https://github.com/lcgamboa/qemu
• davidmonterocrespo24/qemu-lcgamboa: https://github.com/davidmonterocrespo24/qemu-lcgamboa
• qemu/qemu: https://github.com/qemu/qemu

Parent: #21