v0.1.11 engineering prerelease

Engineering prerelease: STM32F103C8 serial OTA and GD32F503VET6 reference build.

• Exactly two target archives: stm32f103c8_firmware.tar.gz and gd32f503_firmware.tar.gz. Each contains bootloader and application images plus SHA256SUMS.
• STM32 application reports FW_VER:0.1.10; without the historical -left suffix. The resident USART3 bootloader supports direct 64-byte-block updates, CRC32 verification, and recovery by retransmitting after an interrupted update. The first bootloader installation still requires SWD. There is no second image slot or automatic rollback.
• The tagged STM32 application was transferred via the A100 serial tunnel to the STM32F103C8 board (UID 0669FF555553787287104058). The 41,860-byte SWD readback matched the release image SHA-256 97610bcb09917f8fa8fd6ad1dd2e3b759549ebeb3f3f27ed28a86b685bf989be. Read-only serial HIL passed 6/6 at 1.5 V input, CHG_EN=0, no battery attached. Earlier tests verified an interrupted update remained in the bootloader and could be retransmitted.
• GD32F503VET6 bootloader and application compile and link, but there is no matching verified board. Its reference pinout is software-defined and charging EN remains disabled. GD32 flash, OTA, and loaded charging have not been tested on hardware.

These are engineering candidates, not production-qualified charging firmware. Flashing remains an operator action.

Factory flashing (STM32F103C8)

• PMIC_all.hex is the merged bootloader + application image for the current STM32F103C8 target. It covers 0x08000000-0x0800B383.
• Flash it once with STM32CubeProgrammer (Full chip erase, then Open file -> PMIC_all.hex -> Start Programming, Verify on) or J-Flash (Program & Verify).
• The original two-file flow (boot.hex at 0x08000000 + ChargeBAT.hex at 0x08001000) remains valid.
• SHA256: 76d0229c32a9c3d2ed99f97c67fe88dffa8d1de8d39308cb62e87824c635d069