feat(kiosk): companion remote drives app iframes via trusted CDP input

Companion tap/scroll/type now works INSIDE cross-origin app iframes and
kiosk tabs. The web relay synthesizes untrusted DOM events in the top
document, which can never cross an origin boundary — so apps served
through the appgate were dead to the remote. The kiosk Chromium now
exposes a loopback-only CDP port (default origin check intact, no
--remote-allow-origins) and a backend bridge (api/handler/cdp.rs)
dispatches validated companion input as Input.dispatchKeyEvent /
dispatchMouseEvent / mouseWheel — trusted events that hit-test through
any frame, move real focus, and insert text like a physical device.

- Session keeper self-heals across kiosk Chromium restarts; inert on
  nodes without a kiosk unit (falls back to the existing relay path).
- The kiosk relay subscriber self-tags (?kiosk=1) and the backend mutes
  its key/click/scroll messages while the bridge is live, so input never
  applies twice; cursor moves still flow for the on-screen cursor.
- While companion input is active the native OS pointer is hidden
  (cursor:none, auto-restores 30s after the last event) so the dead
  physical-mouse cursor doesn't sit next to the virtual one.
- docs/tv-input-iframe-apps.md scope note updated: gamepad keys stay on
  uinput; CDP is for companion pointer/typing only.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

image-recipe/configs/archipelago-kiosk-launcher.sh

@@ -291,7 +291,14 @@ while true; do
       --disable-metrics-reporting \
       --disable-domain-reliability \
       --js-flags="--max-old-space-size=256" \
+      --remote-debugging-port=9222 \
       --user-data-dir=/var/lib/archipelago/chromium-kiosk
+      # --remote-debugging-port binds to 127.0.0.1 only. It feeds the
+      # backend's CDP input bridge (api/handler/cdp.rs), which dispatches
+      # companion-app remote input as TRUSTED browser events — the only way
+      # taps/keys/scrolls reach inside cross-origin app iframes. Chromium's
+      # default origin check stays on (no --remote-allow-origins), so web
+      # pages cannot open the debug socket.
     sleep 3
 done