#152: the real hole -- glass/RIO rigs had NO torso-centre control; wire pod button 0x42

The reported "torso no longer recentres on its own" decomposed into two parts:
the auto-recentre in Mid/Adv was never authentic (it was the stuck-centerCommand
bug acting as a phantom feature since ~674 -- analysis on the ticket, awaiting
Oracle's 1995-memory verdict), but underneath it sat a REAL defect: with the
phantom gone, a glass/RIO player had no way to recentre the torso at all.

WHY.  The only centerCommand writer lived inside the desktop key-bridge block,
which is OFF whenever a RIO/PadRIO is present -- glass and the pod both.  The
pod's dedicated CENTER button (0x42, "the shipped .RES name", UP arrow via
bindings.txt) reached nothing: benched two scripted 0x42 holds on the RIO path,
ctrCmd=0 throughout, twist parked forever.  (Keyboard X/NumPad5 recentred only
as a side effect of ALL-STOP -- you could not recentre without stopping.)

FIX, two pieces, both existing patterns:
  * L4PADRIO::EmitButton -- the documented single chokepoint every button
    source funnels through -- publishes the 0x42 HOLD state
    (gBTTorsoCenterHeld), exactly the 0x3F ReverseThrust precedent.
  * mechmppr gains ONE unified centerCommand writer, deliberately OUTSIDE the
    key-bridge gate (the same placement lesson as the mode-cycle hook):
    hold = torsoCenter(@0x154 databound) OR gBTTorsoCenterHeld(0x42) OR the
    one-frame X pulse; asserts while held, clears on release.  Single writer
    == the sources can never stomp each other's clear.

BENCHED (scratchpad/night14/center42.sh, RIO path, bridge off):
  before: ctrCmd=0 in all samples across two 0x42 holds; twist parked at 1.478
  after:  hold -> ctrCmd=1 recen=1, twist slews 2.22->0.44 at the authored
          0.87 rad/s; twist input DURING the hold cancels sim-side (authentic);
          release clears; no button -> aim holds (authentic Std/Vet).

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

scratchpad/night14/center42.sh

@@ -0,0 +1,26 @@
+#!/usr/bin/env bash
+# #152: is the AUTHENTIC torso-CENTER button (0x42) alive on the RIO/glass path
+# (key bridge OFF)?  Cycle to Standard, deflect/release the twist axis, and
+# hold 0x42 during release windows.  ctrCmd=1 while held + twist slewing to 0
+# = route works (ticket becomes player education).  ctrCmd stuck 0 = the
+# streamed 0x42 route is dead on glass and needs the forward implemented.
+set -x
+. /c/git/bt411/scratchpad/night6/bench_common.sh
+cd /c/git/bt411/content || exit 1
+taskkill //F //IM btl4.exe > /dev/null 2>&1
+sleep 2
+rm -f c42_a.log
+bt_expert_egg MP.EGG C42.EGG
+sed -i "s/^map=.*/map=grass/; s/^time=.*/time=day/; s/^vehicle=.*/vehicle=madcat/" C42.EGG
+( export BT_MODECYCLE_EVERY=400 BT_TWIST_PULSE=150
+  export BT_BTNTEST=0x42,900,1150 BT_BTNTEST2=0x42,1500,1750
+  export BT_TORSO_LOG=1 BT_KEY_NOFOCUS=1 BT_KEY_BRIDGE=0
+  bt_launch c42_a.log C42.EGG 0x03 )
+sleep 130
+bt_kill_ours; sleep 2; taskkill //F //IM btl4.exe > /dev/null 2>&1; sleep 3
+echo "============ RESULT ============"
+grep -a "\[mode\] control mode" c42_a.log | head -4
+echo "--- ctrCmd seen (want some =1 during the 0x42 holds) ---"
+grep -ao "ctrCmd=[01]" c42_a.log | sort | uniq -c
+echo "--- twist trajectory around the first hold ---"
+grep -aE "twistpulse|ctrCmd=1" c42_a.log | head -8