feat: render minimal flight OSD from supervisor snapshots (#3)

deploy/config.yml

@@ -16,6 +16,15 @@ video:
   threshold: -922    # first 5% of CH6 knob remains management/off
   command: fpv-video
 
+osd:
+  # Flight OSD snapshots for the kiosk overlay: final RC channels, arm
+  # state, requested CH6 WFB power and decoded-video presence, published
+  # to tmpfs without blocking the UART path. The display process must read
+  # the same path (its -osd-state flag defaults to the value below).
+  state_path: /run/groundstation/osd-state.bin
+  arm_index: 4       # CH5/AUX1, zero-based
+  armed_threshold: 0
+
 logging:
   enabled: true
   path: /var/log/groundstation/groundstation.log