feat(registry): spiPanelId — a board declares its display's autodetect identity

Vendor autodetects read the panel's RDDID with the display's own CS and
reject or misdetect the board on the bus's idle 0xFF. The answer is board
DATA (which CS, which id byte), not bridge code, so it moves to the def:
the M5Stack Core is {14, 0xE3}, the Cardputer ADV {37, 0x85}. Bridges that
support the probe consume it generically.

frontend/src/lib/proBoardRegistry.ts

@@ -105,6 +105,15 @@ export interface ProBoardDef {
    *  setMicrophoneSource (I2S RX sample injection): shows the canvas-header
    *  Mic toggle that streams the computer's microphone into it. */
   builtInMicrophone?: boolean;
+  /** Display-controller identity for panel autodetect probes. Vendor
+   *  libraries (M5GFX and friends) identify a board by reading the panel's
+   *  RDDID over SPI with the display's own chip-select — and reject the
+   *  board, or misdetect it as something else entirely, when the answer is
+   *  the bus's idle 0xFF. A bridge that supports this answers `idByte` on
+   *  MISO while `csPin` is low. Board DATA, not bridge code: the M5Stack
+   *  Core is `{ csPin: 14, idByte: 0xE3 }` (ILI9342C), the Cardputer ADV
+   *  `{ csPin: 37, idByte: 0x85 }` (ST7789V2). */
+  spiPanelId?: { csPin: number; idByte: number };
   /** Board carries an IMU whose bridge implements setImuAcceleration /
    *  setImuGyro: shows the canvas-header tilt pad. Without it the emulated
    *  part faithfully reports the board lying flat for the whole run. */