Add shared emulator services, waveform generation and STM32 USB boot ports

c/set-protocol/ports/stm32g474-periph/README.md

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+# STM32G474RB emulator peripheral port
+
+Board adapters for the common UMP/TMS/IGBT server and waveform generator.
+All peripheral source files have detailed Russian comments matching the F407 port.
+The shared algorithms, codecs and register map stay in `../../src`.
+
+- `board.c`: application VTOR 0x08010000; HSI16/PLL 160 MHz, APB1 80 MHz;
+  HSI48/CRS USB; board GPIO and 1 ms model ticks.
+- `transport.c`: USART2 PA2/PA3 RTU, optional RS485 DE PB15;
+  FDCAN1 PB8/PB9, Classic CAN, extended IDs, bounded polling and TX timeout.
+- `wave_hal.c`: PA4 DAC1_CH1, TIM6, DMA1_Channel1 with DMAMUX DAC1 request;
+  2..4096 samples in SRAM1/2, exact timer division, maximum 1 MS/s.
+- `main.c`: service ordering and deferred reboot into the G474 USB bootloader.
+
+IGBT input bits 0..7 use PB0/PB1/PB2/PB10/PB11/PB12/PB13/PB14;
+output bits use PC0..PC7. SWD, SWO and USB pins are preserved.
+Clock, addresses and RS485 mode come from the board-supplied `board_config.h`.
+The default internal clock does not guarantee CAN or waveform accuracy over
+all temperature conditions; use a verified 24 MHz HSE source when required.
+
+The consumer supplies `board.h`, `transport.h`, `wave_hal.h`, `emulator.h`,
+G4 HAL configuration and the common model composition. The reference project
+is `Nucleo_G474RB` in the emulator repository. Compile `EMU_CAPACITY=400`:
+each 32000-byte archive bank fits the MCU's 32 KiB CCM/96 KiB SRAM layout.
+DMA samples stay in SRAM1/2. No F407 peripheral implementation is compiled.
+
+Link at 0x08010000 with a 64 KiB Flash limit; install the separate G474RB
+USB bootloader first. Require 128 KiB silicon, DBANK=0, BFB2=0 and no bank swap.
+The firmware rejects mismatched geometry before peripheral initialization.
+Reuse `../stm32g474-usb-boot/boot_usb_port.c` and `boot_request.c` with the
+shared USB CDC transport. Device model: STM32G474RB-EMU-EXPERIMENT.
+
+Host tests validate the shared software; peripheral timing and electrical
+behavior have not yet been validated on a physical board.