wifi: omit empty info snapshot and tidy up

- Info.WiFi uses json "wf" with omitempty so systems without Wi-Fi no
  longer store/broadcast "wifi":null
- move osascript exec into wifi_darwin.go; drop unused commandRunner
- share strongest-connection logic between table cell and sorting
- trim agent/wifi README

internal/site/src/components/systems-table/systems-table-columns.tsx

@@ -38,7 +38,7 @@ import {
 	secondsToUptimeString,
 } from "@/lib/utils"
 import { batteryStateTranslations } from "@/lib/i18n"
-import { connectedWiFi, strongestWiFiSignal } from "@/lib/wifi"
+import { connectedWiFi, strongestWiFi, strongestWiFiSignal } from "@/lib/wifi"
 import type { SystemRecord } from "@/types"
 import { SystemDialog } from "../add-system"
 import AlertButton from "../alerts/alert-button"
@@ -358,12 +358,10 @@ export function SystemsTableColumns(viewMode: "table" | "grid"): ColumnDef<Syste
 			sortUndefined: "last",
 			cell(info) {
 				const connections = connectedWiFi(info.row.original)
-				if (!connections.length) {
+				const strongest = strongestWiFi(connections)
+				if (!strongest) {
 					return null
 				}
-				const strongest = connections.reduce((best, current) =>
-					(current[1].r ?? Number.NEGATIVE_INFINITY) > (best[1].r ?? Number.NEGATIVE_INFINITY) ? current : best
-				)
 				const displayedConnections = viewMode === "table" ? [strongest] : connections
 				const title = connections
 					.map(([id, wifi]) => `${id}${wifi.s ? ` (${wifi.s})` : ""}: ${wifi.r === undefined ? "—" : `${wifi.r} dBm`}`)

internal/site/src/lib/wifi.test.ts

@@ -2,7 +2,7 @@ import { expect, test } from "bun:test"
 import { connectedWiFi, strongestWiFiSignal, wifiColor } from "./wifi"
 import type { SystemInfo } from "@/types"
 
-const system = (wifi?: SystemInfo["wifi"], status: "up" | "down" = "up") => ({ status, info: { wifi } as SystemInfo })
+const system = (wf?: SystemInfo["wf"], status: "up" | "down" = "up") => ({ status, info: { wf } as SystemInfo })
 
 test("current state gates panel, not retained history", () => {
 	expect(connectedWiFi(system())).toEqual([])

internal/site/src/lib/wifi.ts

@@ -3,14 +3,22 @@ import type { SystemRecord, WiFi } from "@/types"
 // Current system info is independent of the selected historical chart window.
 // No fallback to history: missing data, disconnect and offline all hide the panel.
 export function connectedWiFi(system: Pick<SystemRecord, "status" | "info">): [string, WiFi][] {
-	return system.status === "up" ? Object.entries(system.info?.wifi ?? {}).sort(([a], [b]) => a.localeCompare(b)) : []
+	return system.status === "up" ? Object.entries(system.info?.wf ?? {}).sort(([a], [b]) => a.localeCompare(b)) : []
+}
+
+/** Strongest connection by RSSI, falling back to the first when none report a signal. */
+export function strongestWiFi(connections: [string, WiFi][]): [string, WiFi] | undefined {
+	let strongest = connections[0]
+	for (const connection of connections) {
+		if ((connection[1].r ?? -Infinity) > (strongest[1].r ?? -Infinity)) {
+			strongest = connection
+		}
+	}
+	return strongest
 }
 
 export function strongestWiFiSignal(system: Pick<SystemRecord, "status" | "info">): number | undefined {
-	const signals = connectedWiFi(system)
-		.map(([, wifi]) => wifi.r)
-		.filter((signal): signal is number => signal !== undefined && Number.isFinite(signal))
-	return signals.length ? Math.max(...signals) : undefined
+	return strongestWiFi(connectedWiFi(system))?.[1].r
 }
 
 export function wifiColor(id: string): string {

internal/site/src/types.d.ts

@@ -39,7 +39,8 @@ export interface WiFi {
 }
 
 export interface SystemInfo {
-	wifi?: Record<string, WiFi> | null
+	/** connected Wi-Fi interfaces */
+	wf?: Record<string, WiFi>
 	/** hostname */
 	h: string
 	/** kernel **/