fix: routing ip rule missing after reboot, busybox compat, skill restructure

Routing fixes (2026-07-14):
- Add missing ip rule 'from 10.11.13.0/24 lookup 100' to hotplug ifup case
- Add UCI network rule persistence so netifd restores it on boot
- Verify ip rule exists in zt-gateway-switch do_force/do_graceful
- Fix BRIDGE_PORTS auto-detect: use /proc/net/dev instead of broken
  awk-over-ip pipeline (busybox awk mishandles exit in compound if)
- Validate bridge port candidate exists as network interface
- Fix setup-routing: use dev br-zt not dev ztX (ZT iface has no IP
  when enslaved to bridge, causing 'Nexthop has invalid gateway')
- Replace ip rule replace (GNU-only) with del+add for busybox

Infrastructure:
- Fix deploy:install stdin starvation: ssh/scp consume pipe data in
  find|while loop; add </dev/null to prevent truncation
- Move luci-dev skill from root/ to skills/ with .agents/skills/ symlink
- Add policy routing and busybox gotcha sections to SKILL.md
- Add diagnostics doc for the routing fix session

mise.toml

@@ -98,8 +98,8 @@ find root/ htdocs/ -type f | sort | while IFS= read -r src; do
         *) echo "SKIP: $src (unknown prefix)"; continue ;;
     esac
     destdir="${dest%/*}"
-    ssh -q "$HOST" mkdir -p "$destdir"
-    scp -O -q "$src" "$HOST:$dest"
+    ssh -q "$HOST" mkdir -p "$destdir" </dev/null
+    scp -O -q "$src" "$HOST:$dest" </dev/null
     echo "    ${src#./}"
     UPLOADED=$((UPLOADED + 1))
 done