pre-ship: resolve the new audio diagnostic gates ONCE instead of per frame

RunSequence and AudioIdleWatcher::Execute run per sequence per frame, so the
BT_ATTRBIND_LOG probes added while chasing #99 were calling getenv ~2700x/sec on
a 15-sequence mech.  Small, but this is the same path the source-pooling fix
(#32) just bought 10% of frame time in, and an unset diagnostic should cost
nothing.  Cached in function-static flags.

Pre-ship smoke (combat, 2 kills, a respawn, clean teardown):
  frame time 7.18 / 8.27 / 8.71 ms  -- matches the post-pooling 7.79ms baseline
  0 asserts, 0 access violations, 0 audio acquireFails

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

scratchpad/night8/preship.sh

@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+# Pre-ship smoke: combat, no diagnostics, measure frame time + confirm no crash.
+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
+sed "s/^map=.*/map=grass/; s/^time=.*/time=day/" MP.EGG > SHIP.EGG
+rm -f preship.log
+export BT_SPAWN_ENEMY=2 BT_AUTOFIRE=1 BT_GOTO=enemy BT_GOTO_STOP=40
+bt_launch preship.log SHIP.EGG 0x03
+sleep 120
+taskkill //F //IM btl4.exe > /dev/null 2>&1
+sleep 2