tools+docs: a crash-free mission run, a capture that caught no geometry, and a correction

ship_capture_window.sh polls for the flight screen and presses F10 the moment it
appears rather than after a fixed sleep. One run gave three results.

First, the mission ran with ZERO crashes through t+152s - the first clean mission
run, where the three before it ended at 13243 / 11898 / 11497 - and it renders
and plays: player ship, starfield, full HUD, no dialog.

Second, the capture armed and wrote its file, so the mechanism works in-mission.

Third, and against expectation, the file holds NO ship geometry. 329KB, 181
deduped draws: 180 of them share a single vertex shader, all stride=28 vcount=3
prim=8 at full-screen coordinates, plus one full-screen quad, and not one draw
has positions outside the 1280x720 rectangle. The budget is not the limit -
kShipCaptureBudget is 8000 and only 181 distinct (vbase, WVP) pairs were seen -
and the scene was definitely drawing. The known-good capture from an earlier
session is 2.9 MB.

Fourth, a correction to the previous commit. It said the cache is "REFUTED as the
cure". Too strong: this run used the IDENTICAL complete cache as tut4 and
produced 0 crashes against tut4's 11497. What four runs support is that a
complete cache is not SUFFICIENT to prevent the storm and that run-to-run
variance dominates a 3-run comparison - not that the cache does nothing.

Next step is static: compare this capture's shape against the known-good one to
find why the 3D draws never reach CaptureShipDrawForRE.

tools/re-capture/ship_capture_window.sh

@@ -0,0 +1,45 @@
+#!/usr/bin/env bash
+# Take a ship capture INSIDE the mission's clean window.
+#
+# The 0x82307128 crash storms the tutorial 56-112s after it starts, but both
+# runs with a warm cache gave ~1 minute of clean, advancing mission first
+# (docs/re/title-crash-stl-tree.md). F10 has to be pressed in there, so this
+# polls for the flight screen and fires immediately rather than on a fixed sleep.
+#
+#   ship_capture_window.sh [outdir]
+set -u
+export HOME=/sylph-home/re SDL_AUDIODRIVER=dummy DISPLAY=:98
+SD="$(cd "$(dirname "$0")" && pwd)"
+OUT="${1:-/sylph-home/re/shipcap}"
+mkdir -p "$OUT"
+rm -f "$OUT"/xenia_ship_capture_*.log
+
+( cd "$OUT" && ATTEMPTS=1 timeout 1500 "$SD/tutorial_launch.sh" "$OUT" > "$OUT/launch.log" 2>&1 ) &
+LAUNCH=$!
+
+win=""
+deadline=$(( SECONDS + 900 ))
+fired=0
+while [ $SECONDS -lt $deadline ]; do
+  sleep 4
+  screenshot /tmp/sc.png >/dev/null 2>&1 || continue
+  s="$(python3 "$SD/screen_id.py" /tmp/sc.png 2>/dev/null | awk '{print $1}')"
+  if [ "$s" = "flight" ] && [ "$fired" -eq 0 ]; then
+    win="$(xdotool search --name 'Xenia-canary' 2>/dev/null | tail -1)"
+    [ -n "$win" ] || { echo "no window"; break; }
+    echo "FLIGHT at ${SECONDS}s -> F10"
+    xdotool windowactivate --sync "$win" 2>/dev/null; sleep 0.5
+    xdotool key F10; sleep 4
+    # A second press: the capture takes one batch of draws, and the first frame
+    # of a mission may not have the ships in it yet.
+    xdotool key F10
+    fired=1
+    sleep 25
+    break
+  fi
+done
+
+echo "--- captures written ---"
+ls -la "$OUT"/xenia_ship_capture_*.log 2>/dev/null || ls -la /sylph-home/re/xenia_ship_capture_*.log 2>/dev/null || echo "(none)"
+wait $LAUNCH 2>/dev/null
+echo "--- crash dumps: $(grep -ac 'CRASH DUMP' "$OUT/canary.stdout" 2>/dev/null) ---"