Module vga_uart_driver

VgaUart— a **synchronous, write-only** façade that lets capsules use ahil::uart::Uart`-style interface while we actually write to the VGA text buffer, not a serial port.

Key design points

• Implements the minimum subset of Transmit required by MuxUart. All writes copy bytes to the global VGA_TEXT then schedule a deferred call to invoke the transmit callback (split-phase contract).
• Receive / abort / re-configure operations just return ErrorCode::NOSUPPORT — VGA is output-only.

Structs

VgaText

UART-compatible wrapper around the VGA text writer.