Bring up the USB gadget link (package 0b, Pi side and talos side)

The Pi presents NCM Ethernet and ACM serial from a configfs gadget, started by
robot-usb-gadget.service before networking. usb0 gets 10.55.0.2/30 with no
gateway through netplan, matched by interface name: a MAC match turns into
PermanentMACAddress= in networkd, which a gadget interface does not have, so it
stayed unmanaged. talos reaches the Pi at 10.55.0.2 (ping ~2.4 ms, SSH works)
through a NetworkManager profile, host/omarchy/robot-usb-link.sh, matched by the
gadget's fixed host MAC.

Also clamp the face's tunable parameters (focus sets a blur radius, persistence
divides) and fps, after a review flagged unvalidated node parameters.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AFN8nRRCiDiMN7ChBpHJhs

pi/netplan-usb0.yaml

@@ -0,0 +1,14 @@
+# The robot's end of the USB link: /etc/netplan/60-usb0.yaml (mode 600).
+# Matched by name: the kernel names the gadget's NCM interface usb0. (A MAC match does not work:
+# netplan matches the *permanent* MAC, which a gadget interface does not have.) No gateway, so the
+# robot never routes its internet traffic through the host; Wi-Fi stays the way out.
+network:
+  version: 2
+  ethernets:
+    usb0:
+      match:
+        name: usb0
+      addresses: [10.55.0.2/30]
+      dhcp4: false
+      dhcp6: false
+      optional: true