Skey: a FIDO2 security key on the Raspberry Pi Pico

Firmware for the Pico / Pico 2 that acts as a USB FIDO2 authenticator:
CTAP2 and U2F, passkeys, BOOTSEL as the touch button, and clientPIN with
PIN/UV auth protocols 1 and 2. A host simulator runs the same core so the
python-fido2 test suite exercises it without hardware.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

firmware/tusb_config.h

@@ -0,0 +1,20 @@
+#ifndef TUSB_CONFIG_H
+#define TUSB_CONFIG_H
+
+#define CFG_TUSB_RHPORT0_MODE (OPT_MODE_DEVICE | OPT_MODE_FULL_SPEED)
+
+#ifndef CFG_TUSB_OS
+#define CFG_TUSB_OS OPT_OS_NONE
+#endif
+
+#define CFG_TUD_ENDPOINT0_SIZE 64
+
+// One HID interface: the FIDO CTAPHID transport.
+#define CFG_TUD_HID 1
+#define CFG_TUD_HID_EP_BUFSIZE 64
+#define CFG_TUD_CDC 0
+#define CFG_TUD_MSC 0
+#define CFG_TUD_MIDI 0
+#define CFG_TUD_VENDOR 0
+
+#endif