R-50 Phase A: host-install v1.19.0 island default + hub version sync

- felhom-host-install v1.19.0: portless vmbr9 island bridge, appliance binds
  local_api on 169.254.253.1:8443, writes island_bridge/island_guest_addr,
  pins lan_resolver.host_ip to the LAN IP (Finding-1). --no-island opt-out.
- hub hostInstallVersion 1.16.0 -> 1.19.0 (F-1 sync). hostinstall_gates PASS.
- Pairs with agent v0.96.0 (attaches guest net1). byo unchanged.
Coupling: island install requires agent >= 0.96.0 (vouch first).

scripts/CHANGELOG.md

@@ -1,5 +1,24 @@
 # Felhom scripts — Changelog
 
+## felhom-host-install v1.19.0 — R-50 island control plane is the appliance default (2026-07-25)
+
+Implements Phase A of the R-50 island bridge (spike GO, `documentation/audits/SPIKE-island-bridge-2026-07-25.md`).
+A fresh **appliance** install is now born immune to F1 (a LAN/DHCP/site move can no longer take the
+control plane down). **byo is unchanged**; an explicit `--bridge-ip` or `--no-island` keeps the LAN bind.
+
+- New `ensure_island_bridge()` creates a portless host-internal bridge `vmbr9` (`169.254.253.1/30`),
+  idempotently, before the agent binds it. Portless = no physical port, so the /30 cannot collide with
+  any customer LAN and survives any renumber. vmbr0 untouched.
+- `step_agent_config` (appliance default): `local_api.listen_addr` → `169.254.253.1:8443`; writes
+  `local_api.island_bridge`/`island_guest_addr` (the agent ≥ 0.96.0 attaches the guest's `net1` from
+  these); and pins `lan_resolver.host_ip` to the **LAN** IP explicitly — **Finding-1**: without it the
+  agent derives the DNS listen-addr from `listen_addr` and silently moves LAN DNS onto the island.
+- `--no-island` opt-out; `--bridge-ip` still overrides. `configs/felhom-localapi-firewall.example`
+  (agent repo) rewritten — the portless island bind IS the LAN close.
+- **Coupling:** this install REQUIRES agent ≥ 0.96.0 (older agents ignore the island fields → no net1 →
+  broken control plane). Vouch 0.96.0 before island installs go live. Hub `hostInstallVersion` synced to
+  1.19.0 (F-1). Existing boxes migrate via `documentation/runbooks/RUNBOOK-island-migration.md`.
+
 ## ISO train v1.25.0 — the belt goes fleet-wide, the repo goes free, the screen learns ő, fresh boxes boot at the floor (2026-07-23)
 
 Four rulings from 2026-07-23. host-install **1.17.0 → 1.18.0**, build-felhom-iso **1.24.0 → 1.25.0**,