#146 respawn: release the DESKTOP throttle -- and close #137, which was never a bug

#137 ("respawn came back with MYOMERS heat MAXED", Oracle; "overheating
generator D", Sauron) sent us through a full two-sided audit of Mech::Reset
and the whole RTIS chain.  Both sides were correct.  The answer was in the
field log all along, one line after the reset:

    [respawn] Mech::Reset 3:30 healed+moved to (...) alive=1
    [techstat] ... every live condition CLEARED
    [techstat] Myomers condition 3 SET        <- Overheating, immediately
    [mppr] in thr=1 -> ...
    [gaitSM] cycleSpeed=14.6 state=12         <- already RUNNING
    [techstat] Condenser5 condition 3 SET     <- "dumping into coolant loop 5"
    [techstat] GeneratorD condition 3 SET     <- Sauron's generator D

The mech respawns STILL UNDER POWER and earns the heat honestly.  Two facts
close it:

1. condition 3 is an OPERATING flag, not an alarm.  Census over one match:
   LLaser_2 33 SET / 33 CLEARED, LLaser_1 31/31, SRM4 26/26, PPC_2 18/18 --
   every volley trips it and clears it.  EVERY subsystem is balanced
   (GeneratorD 5/4, Myomers 5/4, Condenser5 1/1; the extra SET is only the
   log ending mid-heat).  cond 6 BadPower behaves the same (Myomers 8/8).
   Nothing latches.  A post-respawn SET is not evidence of anything.

2. Mech::Reset's subsystem loop starts at index 2 and the ControlsMapper is
   index 0, so the throttle is never reset -- and the BINARY does the same.
   That is right for a pod: the throttle is a PHYSICAL lever still under the
   pilot's hand.  Respawning under power is authentic and stays.

Oracle's read that the myomer heat rate "felt right" was correct.

WHAT IS a real defect (#146), desktop only: the glass bridge merely EMULATES
that lever, with the static ramp accumulator sLever (mech4.cpp:3250) zeroed
ONLY by the X all-stop and a direction-crossing snap.  A pad/keyboard pilot
is physically holding nothing and cannot see the lever, so they respawned at
speed for no reason they could perceive -- and ate the heat load above.  The
Thrustmaster/RIO path was never affected: InterpretControls (@004d2150)
rebuilds throttlePosition every frame from the databound throttleForward.

Fix: queue the existing all-stop at Mech::Reset, reusing the proven path
(it already clears the zero-crossing detent too).  LOCAL VIEWPOINT MECH ONLY
-- gBTDrive is the local bridge's state and Reset also runs for replicants,
so an ungated write would all-stop the player whenever a REMOTE mech
respawned.  Pod-safe besides: with a RIO present the key bridge is off and
gBTDrive.throttle is never read.  BT_NO_RESPAWN_THROTTLE_RELEASE=1 reverts.

Benched 2-node (scratchpad/night13/throttlerespawn.sh): the release fires
1:1 with local respawns on both nodes independently (A 2/2, B 1/1) and never
spuriously.  HONEST LIMIT: the viewpoint gate was NOT stressed -- B ran
Mech::Reset 0 times for A's mech, so the remote-respawn path never fired.
The gate is correct by construction (the isPlayerMech idiom), not proven.
BT_AUTODRIVE cannot test the lever itself (forced mode reads forcedThrottle,
never sLever), and the zeroing path is the X button, proven in the field.

Also keeps BTReportHeatAtReset (heat.cpp, BT_HEAT_LOG): the [heat-t] census
runs on a 5s timer, far too coarse to sample AT the reset.  It is what
proved every roster subsystem including all six Condensers sits at T=77
start=77, and it corrected an earlier false negative from filtering on
IsDerivedFrom(HeatSink).

KB: context/decomp-reference.md gains the routine/self-clearing condition
semantics + this post-mortem, so it is not re-chased; cross-ref in
context/gauges-hud.md.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018SgmXGNMXavXiafKXf9MDC

game/reconstructed/mech4.cpp

@@ -2249,6 +2249,54 @@ void
 		BTRecomputeCondenserValves((Entity *)this);
 	}
 
+	// #137 forensic: sample every heat-bearing subsystem's temperature AT the
+	// reset, so "respawn came back with heat MAXED" can be split into "the
+	// reset did not clear it" vs "it climbs again immediately".
+	{
+		extern void BTReportHeatAtReset(void *mech_v);
+		BTReportHeatAtReset((void *)this);
+	}
+
+	// --- DESKTOP THROTTLE RELEASE (#146) -- PORT LAYER, desktop-only ---------
+	//     The pod's throttle is a PHYSICAL lever and the binary deliberately
+	//     leaves it alone across a respawn: Reset's subsystem loop starts at
+	//     index 2 and the ControlsMapper is index 0, so a pod pilot comes back
+	//     under whatever power their hand is still holding.  Authentic; it stays.
+	//
+	//     The desktop bridge only EMULATES that lever, with the persistent ramp
+	//     accumulator sLever below -- and a pad/keyboard pilot is physically
+	//     holding nothing, with the lever position invisible to them.  So they
+	//     respawned at speed for no reason they could see, and the mech earned a
+	//     real heat load straight out of the drop zone (myomers -> Condenser5 ->
+	//     GeneratorD all tripping Overheating inside 1-2s).  That is the true
+	//     cause of the "#137 respawn came back with heat MAXED" reports -- the
+	//     reset itself was always clean.  Field-diagnosed from Sauron's
+	//     2026-08-06 log, which reads thr=1 / cycleSpeed=14.6 AT the reset.
+	//
+	//     Reuse the existing all-stop path instead of touching sLever directly:
+	//     it already zeroes the lever AND clears the zero-crossing detent, and it
+	//     lives inside the virtual-controls block that owns that state.
+	//
+	//     LOCAL VIEWPOINT MECH ONLY -- gBTDrive is the local bridge's state and
+	//     Reset also runs for replicants, so an ungated write here would all-stop
+	//     the player every time a REMOTE mech respawned.  (Same guard idiom as
+	//     the isPlayerMech test in PerformAndWatch.)  Pod-safe besides: with a RIO
+	//     present mechmppr's key bridge is off (BTRIODevicePresent, mechmppr.cpp
+	//     :672) and gBTDrive.throttle is never read at all.
+	//     BT_NO_RESPAWN_THROTTLE_RELEASE=1 reverts.
+	if (application != 0 && (Entity *)this == application->GetViewpointEntity())
+	{
+		static const int s_releaseThrottle =
+			getenv("BT_NO_RESPAWN_THROTTLE_RELEASE") ? 0 : 1;
+		if (s_releaseThrottle)
+		{
+			gBTDrive.allStop = 1;
+			if (getenv("BT_DEATH_LOG"))
+				DEBUG_STREAM << "[respawn] desktop throttle released (all-stop queued)\n"
+					<< std::flush;
+		}
+	}
+
 	// --- locomotion pre-run + interest gates (a reset master must tick) ---
 	SetPreRunFlag();
 	if (interestCount == 0) interestCount = 1;