fix(client/net): split the receipt stamp from the pull + bleed standing latency

The two-pair investigation (wired Mac clients stuck at a rock-steady
~18-19 ms "network" that survived the load ending and cleared only on
reconnect) exposed two structural gaps, one of measurement and one of
recovery:

- Receipt was stamped at the hand-off PULL (Swift nextAU, pf-client-core,
  Android decode loops), not at reassembly completion — so any client-side
  standing state between the reassembler and the pull read as NETWORK
  latency, undiagnosable from the HUD. ABI v9: `PunktfunkFrame`/`Frame`
  grow `received_ns`, stamped by `Session::poll_frame` as the AU crosses
  the session boundary. Every embedder now uses the core stamp; the Apple
  client keeps the pull instant as `AccessUnit.pulledNs` and shows the
  receipt→pull wait as its own "client queue" term (detailed HUD tier from
  2 ms + a `queue_p50` stats-log field). Decode stages keep their pull
  anchor on all platforms, so no historical stage shifts meaning.

- The jump-to-live detectors deliberately ignore anything under 6 queued
  frames / 400 ms behind — so a small, constant, loss-free elevation (a
  sub-frame standing backlog, or a stale clock offset after a wall-clock
  step/slew) is carried for the rest of the session. New third detector
  (`StandingLatency`, unit-tested ladder): window-MIN one-way delay
  ≥ 10 ms above the session floor with zero loss for ~4.5 s escalates
  gently — a free clock re-sync first (an applied re-sync re-bases the
  floor), then at most 3 flush+keyframe bleeds sharing the jump-to-live
  cooldown, then a loud disarm naming what it means. Loss windows reset
  the run: congestion belongs to FEC/ABR, not this detector.

Also: mid-stream re-sync apply/discard logs debug→info — they are the
forensic trail for the stale-offset case and were invisible in the field.

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

clients/apple/Sources/PunktfunkClient/Session/SessionModel.swift

@@ -102,6 +102,12 @@ final class SessionModel: ObservableObject {
     @Published var decodeValid = false
     @Published var displayP50Ms = 0.0
     @Published var displayValid = false
+    /// Client-queue wait: core reassembly receipt → the pump's pull (`AccessUnit.pulledNs −
+    /// receivedNs`, ABI v9 receipt split — the 2026-07 two-pair investigation). ~0 on a healthy
+    /// stream; a persistent value is a client-side standing backlog that used to hide inside
+    /// "network". Shown in the detailed tier only when it says something (≥ ~2 ms).
+    @Published var clientQueueP50Ms = 0.0
+    @Published var clientQueueValid = false
     /// The measured OS present floor (design/apple-presentation-rebuild.md): the deadline
     /// engine's vend→glass pipeline depth — an OS property no client can pace under (~2 refresh
     /// intervals composited; would read ~1 under direct-to-display). The HUD subtracts it from
@@ -147,6 +153,9 @@ final class SessionModel: ObservableObject {
     let endToEnd = LatencyMeter()
     let decodeStage = LatencyMeter()
     let displayStage = LatencyMeter()
+    /// Client-queue sampler (see `clientQueueP50Ms`) — fed per AU by the stream view's onFrame,
+    /// drained by the same 1 s tick as the stage meters.
+    let clientQueue = LatencyMeter()
     /// The OS present floor sampler (see `osFloorP50Ms`) — fed one sample per display-link
     /// update by the deadline engine, drained by the same 1 s tick as the stage meters.
     let presentFloor = LatencyMeter()
@@ -489,6 +498,7 @@ final class SessionModel: ObservableObject {
         endToEndValid = false
         decodeValid = false
         displayValid = false
+        clientQueueValid = false
         osFloorValid = false
         lostFrames = 0
         lostPct = 0
@@ -679,6 +689,12 @@ final class SessionModel: ObservableObject {
                 } else {
                     self.osFloorValid = false
                 }
+                if let q = self.clientQueue.drain() {
+                    self.clientQueueP50Ms = q.p50Ms
+                    self.clientQueueValid = true
+                } else {
+                    self.clientQueueValid = false
+                }
                 // Mirror the window to the unified log (see statsLog) — one line per second,
                 // stages in ms, only while frames actually flowed. `fps` counts RECEIVED AUs;
                 // `presents` counts frames that reached glass (the display meter's sample count)
@@ -691,7 +707,7 @@ final class SessionModel: ObservableObject {
                     let line = String(
                         format: "fps=%d presents=%d e2e_p50=%.1f e2e_p95=%.1f hostnet_p50=%.1f "
                             + "decode_p50=%.1f display_p50=%.1f lost=%d "
-                            + "floor_p50=%.1f display_adj=%.1f e2e_adj=%.1f",
+                            + "floor_p50=%.1f display_adj=%.1f e2e_adj=%.1f queue_p50=%.1f",
                         frames,
                         displayWindow?.count ?? 0,
                         self.endToEndValid ? self.endToEndP50Ms : -1,
@@ -702,7 +718,8 @@ final class SessionModel: ObservableObject {
                         lost,
                         self.osFloorValid ? self.osFloorP50Ms : -1,
                         self.displayValid ? self.displayAdjP50Ms : -1,
-                        self.endToEndValid ? self.endToEndAdjP50Ms : -1)
+                        self.endToEndValid ? self.endToEndAdjP50Ms : -1,
+                        self.clientQueueValid ? self.clientQueueP50Ms : -1)
                     statsLog.info("\(line, privacy: .public)")
                 }
             }