feat(tui): inline detail panel below monitors table

Press i to toggle a compact detail panel below the monitors+logs
split. Shows status, latency, uptime, state changes, sparkline, and
key hints in ~6 lines. Auto-updates when cursor moves between
monitors. h/s/e keys work from the inline detail for history, SLA,
and edit. Escape closes the panel.

No more full-screen detail takeover for the common case. The old
stateDetail path remains for h/s sub-views which still go full-screen.

internal/tui/tui.go

@@ -179,7 +179,7 @@ type Model struct {
 	lastTabLoad        time.Time // last dispatch of loadTabDataCmd (throttle)
 	tabSeq             int       // seq of the newest issued tab-data load
 
-	// detail-panel state-change history, loaded on enter so View does no DB IO
+	detailOpen          bool
 	detailChanges       []models.StateChange
 	detailChangesSiteID int