correct the record: the 2026-08-10 boot wedges were the USB-serial adapter hanging an unbounded overlapped write, NOT print-deadlock (confounded A/B, retracted); pod runbook gets the full COM1/FTDI diagnosis + remote minidump procedure

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

engine/MUNGA_L4/L4RIO.cpp

@@ -1364,13 +1364,15 @@ Logical
 	Word		errors;
 
 	//
-	// [rio] link-health TRACKING -- pure arithmetic, no I/O.  ⚠ NEVER PRINT
-	// FROM THIS PATH: the first version DEBUG_STREAMed here and deadlocked
-	// the process against the PCSPAK RX thread within ~10 s of every
-	// live-RIO boot (2026-08-10 ALPHA-MR: 0-CPU park after "RIO successfully
-	// initialized", A/B-convicted by BT_RIO_LOG=0 booting clean).  The
-	// printer half is BTRioHealthReport() below, called from the glass tick
-	// beside [glassperf] -- a proven-safe stream site.
+	// [rio] link-health TRACKING -- pure arithmetic, no I/O here by design.
+	// CORRECTED HISTORY (2026-08-10): the boot wedges first blamed on prints
+	// from this path were actually the USB-serial adapter dropping its link
+	// with a write in flight -- the unbounded GetOverlappedResult in
+	// PCSerialPacket::SendPacket parked the game (minidump-proven; the
+	// print-deadlock A/B was confounded by the adapter behaving that boot).
+	// The count-here / print-from-the-glass-tick split stays anyway: it
+	// keeps this hot polled path I/O-free and the printer at one known
+	// stream site (BTRioHealthReport below, beside [glassperf]).
 	//
 	if (operational)
 	{