Add Starlink status lines for the physical gateway pane (closes #3)

When the non-VPN physical gateway is a Starlink dish, two lines are shown
under that pane: state, uptime, obstruction and alert count; then pop-ping
latency and drop rate with downlink/uplink throughput. They turn red when
the dish is not connected or an alert is active.

Detection is a TCP connect to the dish's fixed endpoint 192.168.100.1:9200,
bound to the physical interface the same way the latency probes bind. Until
a dish answers nothing is drawn and no status is fetched, so an absent dish
adds no noise. Status comes from the dish's local get_status gRPC call.

Detection and the fetch sit behind a small Client interface; the loop and
the pure Render function are tested with a fake, no dish and no network.

Model: opus-4-8

internal/monitor/export_test.go

@@ -1,7 +1,52 @@
 package monitor
 
+import (
+	"context"
+
+	"git.eeqj.de/sneak/rtnetmon/internal/starlink"
+)
+
 // Test-only accessors exposing unexported state for white-box assertions.
 
+// SetStarlinkClient injects a Starlink client for iface, bypassing the real
+// gRPC dialer so the loop can be driven with a fake.
+func (m *Monitor) SetStarlinkClient(iface string, c starlink.Client) {
+	for _, st := range m.interfaces {
+		if st.Name == iface {
+			m.slPane = st
+			m.slState = &starlinkState{}
+			m.slClient = c
+
+			return
+		}
+	}
+}
+
+// StarlinkEnabled reports whether a Starlink client is configured.
+func (m *Monitor) StarlinkEnabled() bool { return m.slClient != nil }
+
+// StarlinkPaneName returns the name of the pane the Starlink lines attach
+// to, or "" if none.
+func (m *Monitor) StarlinkPaneName() string {
+	if m.slPane == nil {
+		return ""
+	}
+
+	return m.slPane.Name
+}
+
+// StarlinkProbeStep runs one detection step.
+func (m *Monitor) StarlinkProbeStep(ctx context.Context) { m.starlinkProbe(ctx) }
+
+// StarlinkRefreshStep runs one status-refresh step.
+func (m *Monitor) StarlinkRefreshStep(ctx context.Context) { m.starlinkRefresh(ctx) }
+
+// StarlinkSnapshot returns the current Starlink display state: detected,
+// have-status, and the latest status.
+func (m *Monitor) StarlinkSnapshot() (bool, bool, starlink.Status) {
+	return m.slState.snapshot()
+}
+
 // ReachabilityHosts returns the configured reachability hosts.
 func (m *Monitor) ReachabilityHosts() []string { return m.reachabilityHosts }