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/PunktfunkKit/Video/Stage2Pipeline.swift

@@ -1213,7 +1213,9 @@ public final class Stage2Pipeline {
                         let chunkAligned =
                             au.flags & PunktfunkConnection.userFlagChunkAligned != 0
                         let ptsNs = au.ptsNs
-                        let receivedNs = au.receivedNs
+                        // Decode stage starts at the PULL (matching the VT path's FrameContext —
+                        // receipt→pull is the HUD's separate client-queue term, ABI v9 split).
+                        let receivedNs = au.pulledNs
                         let flags = au.flags
                         let submitted = decoder.decode(
                             au: au.data, chunkAligned: chunkAligned, windowSize: windowSize

clients/apple/Sources/PunktfunkKit/Video/VideoDecoder.swift

@@ -32,9 +32,12 @@ public enum ReadyImage: @unchecked Sendable {
 public struct ReadyFrame: @unchecked Sendable {
     /// Host capture clock (the AU's pts), in nanoseconds.
     public let ptsNs: UInt64
-    /// Client `CLOCK_REALTIME` instant the AU was received (`AccessUnit.receivedNs`, threaded
-    /// through the decode via the frame refcon), in nanoseconds. 0 when unknown (a caller that
-    /// didn't stamp receipt) — the decode-stage meter then drops the sample via its sanity guard.
+    /// Client `CLOCK_REALTIME` instant the AU left `nextAU` (`AccessUnit.pulledNs`, threaded
+    /// through the decode via the frame refcon), in nanoseconds — the decode stage's start
+    /// point. (Named for its historical role; since the ABI v9 receipt split the true
+    /// reassembly receipt lives on `AccessUnit.receivedNs`, and receipt→pull is the HUD's own
+    /// client-queue term.) 0 when unknown (a caller that didn't stamp) — the decode-stage meter
+    /// then drops the sample via its sanity guard.
     public let receivedNs: Int64
     /// Client `CLOCK_REALTIME` instant decode completed, in nanoseconds.
     public let decodedNs: Int64
@@ -167,7 +170,11 @@ public final class VideoDecoder: @unchecked Sendable {
         var infoOut = VTDecodeInfoFlags()
         // The AU's receipt instant + wire flags ride through as a retained context; the output
         // callback reclaims it. Retain immediately before submit so no early return can leak it.
-        let ctx = FrameContext(receivedNs: au.receivedNs, flags: au.flags)
+        // The decode stage starts at the PULL (the AU leaving nextAU), not the reassembly
+        // receipt: both consumers — the decode-stage meter and the ABR decode signal — are
+        // specified from the pull, and the receipt→pull wait is the HUD's separate client-queue
+        // term (see AccessUnit.pulledNs).
+        let ctx = FrameContext(receivedNs: au.pulledNs, flags: au.flags)
         let refcon = Unmanaged.passRetained(ctx).toOpaque()
         let status = VTDecompressionSessionDecodeFrame(
             session,