[WIP] Add reliable flashing features and test firmware

[Copilot]

Thanks for asking me to work on this. I will get started on it and keep this PR's description up to date as I form a plan and make progress.

Original prompt

Create a non-destructive feature branch off main and open a pull request implementing the following changes to make flashing reliable, add test firmware, OTA support, and a boot splash. Do NOT delete or alter existing branches. Repository: Crashkeyz/UltimatumCardputerKey.

Summary of changes to implement:

1. platformio.ini

• Set upload_speed default to 115200 for the m5stack-cardputer env.
• Add an optional environment [env:m5stack-cardputer-fast] that keeps upload_speed = 921600.
• Add comments describing OTA upload options and how to enable espota.

2. Reliable esptool flash scripts

• Add scripts/flash_esptool.sh (Linux/macOS): accepts PORT, BIN, BAUD; erases flash; writes firmware using esptool for esp32s3; verifies result; exits non-zero on failure; mark executable.
• Add scripts/flash_esptool.bat (Windows): analogous commands and usage notes.

3. Test firmware

• Add src/test_blink/main.cpp: initializes M5Unified, displays "FLASH OK" and toggles every 500ms; prints "FLASH OK" to Serial at 115200. Compatible with the existing m5stack-cardputer env.

4. OTA example

• Add src/ota_update/main.cpp: M5Unified init, Wi-Fi provisioning options (compile-time via build flags, data partition file, or serial entry), initialize ArduinoOTA (or esp32s3-compatible OTA), print OTA progress/state to Serial and display. Include README in src/ota_update/README.md describing setup and how to use espota (upload_port, password) and platformio.ini example for espota.

5. Boot splash

• Add src/boot_splash/main.cpp or integrate into main startup to display the splash text "HACK THE PLANT!!!" on the M5 display at boot for ~3s and print same message to Serial at 115200. Make the splash text configurable via a #define in a header.

6. README updates

• Add sections "Build and Flash", "Use esptool (recommended if M5 Burner stalls)", "M5 Burner notes", "Test firmware", and "OTA Update" with exact commands and troubleshooting steps.

7. CI workflow

• Add .github/workflows/build-firmware.yml: builds the m5stack-cardputer env on push/PR, and uploads .bin and .elf as artifacts for download.

8. Branch & PR

• Create a new branch named refactor/flash-ota-cleanup from main, push all changes there, and open a pull request from refactor/flash-ota-cleanup into main.
• The PR description should list changed/added files and include testing steps (build, esptool flash, splash check, OTA check). Do NOT assign the PR.

Testing instructions to include in PR description:

• pio run -e m5stack-cardputer
• python -m pip install esptool
• python -m esptool --chip esp32s3 --port /dev/ttyUSB0 --baud 115200 erase_flash
• python -m esptool --chip esp32s3 --port /dev/ttyUSB0 --baud 115200 write_flash -z 0x1000 .pio/build/m5stack-cardputer/firmware.bin
• Verify display shows "FLASH OK" for test firmware and boot splash shows "HACK THE PLANT!!!" on main firmware.
• OTA: document how to provide Wi-Fi credentials and use PlatformIO espota upload; verify new firmware runs after OTA.

Notes:

• Do NOT implement any functionality that would bypass authorization or enable unauthorized access. All OTA updates require passwords and secure provisioning as described in the README.
• Keep changes minimal and well-documented to make review easy.

Please create the PR and respond with the PR URL and a short summary of the files changed and next steps. I will add the Lily repo later when provided to add OTA there as well.

This pull request was created from Copilot chat.

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