Initial commit: NetworkCity — network traffic as a neon city

A native macOS network monitor that renders live traffic as a top-down
neon city: your Mac is downtown, remote orgs are glowing districts, and
traffic is cars of light driving the roads.

Architecture:
- NetworkCityCore: swappable data layer behind a ConnectionSource protocol
  (nettop-backed today), plus pure/tested logic — traffic diffing, org
  classification (reverse-DNS + CIDR), traffic classes, hub-and-spoke
  expansion policy, label anti-overlap, and latency→distance layout.
- NetworkCityApp: SwiftUI + SpriteKit city — auto-expanding districts,
  protocol-coloured cars, click-to-inspect panel, and latency-as-distance
  (districts glide to their measured RTT).
- nettop-probe: CLI proof of the data layer.

44 tests passing.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Sources/NetworkCityApp/Inspection.swift

@@ -0,0 +1,25 @@
+import NetworkCityCore
+
+/// One endpoint's live detail for the inspector panel.
+struct EndpointInfo: Identifiable {
+    var id: String { host }
+    let host: String
+    let rdns: String?
+    let downKBs: Double
+    let upKBs: Double
+    let topClass: TrafficClass
+    let rttMs: Double?
+}
+
+/// A live snapshot of one district, shown when its hub is clicked. Rebuilt each
+/// tick while selected so the panel updates in real time.
+struct OrgInspection: Identifiable {
+    var id: String { key }
+    let key: String
+    let title: String
+    let downKBs: Double
+    let upKBs: Double
+    let endpointCount: Int
+    let endpoints: [EndpointInfo]
+    let processes: [String]
+}