docs: the reseq probe's readings, and the invariants resequencing changes

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tools/mock_udpstreamer.py

@@ -271,10 +271,11 @@ def main():
         type=int,
         default=0,
         help="hold every Nth packet back and send it after the next one that goes out -- "
-        "an inversion on the wire. The receiver takes the later counter first, so the held "
-        "packet no longer advances the counter and is stale by definition: one inversion "
-        "costs one counter gap, one stale packet, and that packet's samples for good. A "
-        "--drop-every that swallows the packet after a held one deepens the inversion "
+        "an inversion on the wire. What the receiver does depends on how late the held "
+        "packet arrives: inside the 20 ms reorder window it is resequenced with no hole; "
+        "past it a hole is committed first and the packet backfills it. "
+        "--reorder-delay-ms controls which path is taken (see its help). "
+        "A --drop-every that swallows the packet after a held one deepens the inversion "
         "rather than cancelling it, since the held packet waits for the next packet "
         "actually sent. 0 = never",
     )