feat(clients): unified stats vocabulary across every client + Moonlight comparison docs

One stat model everywhere (design/stats-unification.md): four measurement
points (capture/received/decoded/displayed), three stages that tile the
interval exactly, and a HUD that shows the addition explicitly —

  end-to-end 14.2 ms p50 · 19.8 p95 · capture→on-glass
  = host+network 9.8 + decode 2.1 + display 2.3

replacing each client's ad-hoc mix of overlapping absolutes (the Apple HUD's
three arrow lines that looked sequential but weren't), mean-vs-median decode
times (Windows/Linux), missing same-host-clock flags (Windows/Linux), and
three different names for the same capture→received measurement (probe's
"reassembled", Apple/Android's "client", Windows/Linux's post-decode "lat").

Per client: Apple threads receivedNs through the VT decode via the frame
refcon bit pattern so the decode stage exists at all (stage-1 fallback
honestly degrades to a capture→received headline); Windows carries
FrameTimes through the existing frame channel to the render thread and adds
e2e p50/p95 post-Present; Linux stamps received at AU pop and rides
decoded_ns on DecodedFrame to the paintable-set site; Android pairs receipt
stamps with MediaCodec output buffers via the codec's pts round-trip (JNI
stats array 14→16 doubles, indexes 0-13 unchanged). fps now uniformly counts
received AUs; lost/(received+lost) per window, hidden at zero.

docs-site gains "Understanding the Stats Overlay": what each line means, why
the equation only approximately sums (percentiles), and a line-by-line
Moonlight/Sunshine matrix — including that Moonlight has no end-to-end
number and its "network latency" is an ENet control RTT, so punktfunk's
headline must not be compared against any single Moonlight line.

Verified here: linux client + probe + core check/clippy/fmt green, android
native cargo-ndk arm64 check green. Pending: Windows CI + on-glass, swift
test on the mac, on-device Android.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

clients/apple/Sources/PunktfunkKit/Views/StreamViewIOS.swift

@@ -50,8 +50,9 @@ public struct StreamView: UIViewControllerRepresentable {
     private let onCaptureChange: ((Bool) -> Void)?
     private let onFrame: (@Sendable (AccessUnit) -> Void)?
     private let onSessionEnd: (@Sendable () -> Void)?
-    private let presentMeter: LatencyMeter?
-    private let presentTailMeter: LatencyMeter?
+    private let endToEndMeter: LatencyMeter?
+    private let decodeMeter: LatencyMeter?
+    private let displayMeter: LatencyMeter?
 
     public init(
         connection: PunktfunkConnection,
@@ -59,24 +60,27 @@ public struct StreamView: UIViewControllerRepresentable {
         onCaptureChange: ((Bool) -> Void)? = nil,
         onFrame: (@Sendable (AccessUnit) -> Void)? = nil,
         onSessionEnd: (@Sendable () -> Void)? = nil,
-        presentMeter: LatencyMeter? = nil,
-        presentTailMeter: LatencyMeter? = nil
+        endToEndMeter: LatencyMeter? = nil,
+        decodeMeter: LatencyMeter? = nil,
+        displayMeter: LatencyMeter? = nil
     ) {
         self.connection = connection
         self.captureEnabled = captureEnabled
         self.onCaptureChange = onCaptureChange
         self.onFrame = onFrame
         self.onSessionEnd = onSessionEnd
-        self.presentMeter = presentMeter
-        self.presentTailMeter = presentTailMeter
+        self.endToEndMeter = endToEndMeter
+        self.decodeMeter = decodeMeter
+        self.displayMeter = displayMeter
     }
 
     public func makeUIViewController(context: Context) -> StreamViewController {
         let controller = StreamViewController()
         controller.onCaptureChange = onCaptureChange
         controller.captureEnabled = captureEnabled
-        controller.presentMeter = presentMeter
-        controller.presentTailMeter = presentTailMeter
+        controller.endToEndMeter = endToEndMeter
+        controller.decodeMeter = decodeMeter
+        controller.displayMeter = displayMeter
         controller.start(connection: connection, onFrame: onFrame, onSessionEnd: onSessionEnd)
         return controller
     }
@@ -84,8 +88,9 @@ public struct StreamView: UIViewControllerRepresentable {
     public func updateUIViewController(_ controller: StreamViewController, context: Context) {
         controller.onCaptureChange = onCaptureChange
         controller.captureEnabled = captureEnabled
-        controller.presentMeter = presentMeter
-        controller.presentTailMeter = presentTailMeter
+        controller.endToEndMeter = endToEndMeter
+        controller.decodeMeter = decodeMeter
+        controller.displayMeter = displayMeter
         if controller.connection !== connection {
             controller.start(connection: connection, onFrame: onFrame, onSessionEnd: onSessionEnd)
         }
@@ -101,10 +106,11 @@ public struct StreamView: UIViewControllerRepresentable {
 public final class StreamViewController: UIViewController {
     public private(set) var connection: PunktfunkConnection?
     private var observers: [NSObjectProtocol] = []
-    /// Record capture→present / decode→present when the stage-2 presenter is active.
-    /// Consulted at start().
-    var presentMeter: LatencyMeter?
-    var presentTailMeter: LatencyMeter?
+    /// Record the unified latency stages (end-to-end / decode / display) when the stage-2
+    /// presenter is active. Consulted at start().
+    var endToEndMeter: LatencyMeter?
+    var decodeMeter: LatencyMeter?
+    var displayMeter: LatencyMeter?
     /// The shared presenter stack: stage-2 (CAMetalLayer sublayer + display link) with the
     /// stage-1 StreamPump → displayLayer path as the Metal-unavailable / DEBUG fallback.
     private let presenter = SessionPresenter()
@@ -285,8 +291,9 @@ public final class StreamViewController: UIViewController {
         presenter.start(
             connection: connection,
             baseLayer: streamView.displayLayer,
-            presentMeter: presentMeter,
-            presentTailMeter: presentTailMeter,
+            endToEndMeter: endToEndMeter,
+            decodeMeter: decodeMeter,
+            displayMeter: displayMeter,
             makeDisplayLink: { CADisplayLink(target: $0, selector: $1) },
             onFrame: onFrame,
             onSessionEnd: onSessionEnd)