External peripheral interface scaffold

This file records product-level external interfaces that are not implemented by the current e1 RTL but must be tracked while padframe, package, and board contracts mature.

Interface	Contract source	Current e1 chip status
Debug/MMIO demo bridge	package/e1-demo-pinout.yaml	Bonded in placeholder QFN64 package
GPIO LEDs/test outputs	package/e1-demo-pinout.yaml	Bonded in placeholder QFN64 package
JTAG/test reservation	package/e1-demo-pinout.yaml	Reserved pins only
WiFi/Bluetooth module	package/wifi-external-interface.yaml	Product scaffold; not bonded in e1 chip; SDIO host, Bluetooth transport ownership, and firmware driver not implemented

Future RTL must not silently consume package pins for product interfaces. Additions should first update the machine-readable package or interface contract, then update padframe and board checks.