Mirror the iOS gateway settings ordering: nav-bar QR scan action,
Scan QR to Pair hero while unpaired, one Add Gateway panel (scan,
setup code + connect, discovered gateways with per-row connect),
paired gateways below, manual host/credential plumbing at the bottom.
Add facts rows (Discovered, Default Agent, Agents, Instance ID) and a
Diagnose action, plus a deterministic 'gateway' screenshot scene.
Closes#106186