tools: F5 probe -- a second A during the title build-in

Presses A once to skip the attract video, then again during the build-in,
and records the press instant so a press that lands late is reported rather
than silently reinterpreted. Blind timing is the weak point: the build-in is
~5 s wide and run pacing has been seen to vary 2x.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Jc4pciRArGHfxGGhEbwp5t

tools/re-capture/f5_snap_or_accelerate.sh

@@ -0,0 +1,56 @@
+#!/usr/bin/env bash
+# F6 unit 2 -- capture the TITLE's build-in and read the sweep's drawn alpha.
+#
+# Discriminator: pteff03's LEAF declares alpha 255 from its own t=0, while its
+# PARENT ramps 0->255 across t=70..100. So in the drawn vertex colour:
+#     flat 255 throughout  => the parent is NOT multiplied in
+#     a ramp 0->255        => it IS
+# That also settles the port's own flagged ambiguity, whose stated separating
+# interval (t=100..238) is the same one F6 is about.
+#
+# Simpler than the menu probe on purpose: ONE A press to skip the attract video,
+# then no further input, so the title builds in undisturbed and stays.
+set -u
+export HOME=/sylph-home/re SDL_AUDIODRIVER=dummy DISPLAY=:98
+export XENIA_PAD_FILE=/tmp/xenia_pad.txt
+OUT="${1:-/sylph-home/re/f5}"; mkdir -p "$OUT"; rm -f "$OUT"/xenia_re_ui_draws_*.log
+pad(){ printf '%s' "$1" > "$XENIA_PAD_FILE.tmp"; mv "$XENIA_PAD_FILE.tmp" "$XENIA_PAD_FILE"; }
+pad ""
+( cd "$OUT" && nohup run-canary --log_ui_draws=true \
+    --ui_draw_capture_frames=6000 --ui_draw_capture_max=1500000 \
+    >"$OUT/canary.stdout" 2>"$OUT/canary.stderr" & )
+sleep 8
+win="$(xdotool search --name "Xenia-canary" | tail -1)"
+[ -n "$win" ] || { echo "FATAL: no Xenia window"; pkill -x xenia_canary; exit 1; }
+xdotool windowactivate "$win" 2>/dev/null; xdotool key --window "$win" F10; xdotool key F10
+echo "armed at ${SECONDS}s"
+
+sleep 12; pad "press=A"; sleep 0.4; pad ""; echo "A (skip video) at ${SECONDS}s"
+
+# ⚠️ ARMING IS NOT CONFIRMED BY SENDING THE KEY. Twice now a probe has printed
+# "armed", pressed on, and written no draw log at all -- once because the window
+# lookup failed, once with the window found and the key sent. A probe that cannot
+# confirm its own instrument is recording is a probe whose negatives mean nothing.
+# So: wait for the log to exist AND grow, and abort loudly if it does not.
+for _ in $(seq 1 45); do
+  sz=$(stat -c %s "$OUT"/xenia_re_ui_draws_*.log 2>/dev/null | head -1 || echo 0)
+  [ "${sz:-0}" -gt 0 ] && break
+  sleep 1
+done
+[ "${sz:-0}" -gt 0 ] || { echo "FATAL: armed but no draw log after 45s -- not recording"; pkill -x xenia_canary; exit 1; }
+echo "logging confirmed at ${SECONDS}s (${sz} bytes)"
+
+# --- F5: a SECOND A during the title build-in ---------------------------
+# Discriminator (brief): a snap shows no intermediate alphas, an acceleration
+# does. Press 2 must land while the build-in is still running -- after the
+# sweep is up (title t>=100) and before the settle (~t=236). Blind timing is
+# the weak point, so the press instant is RECORDED and checked post hoc; a
+# press that lands late is reported as such, not silently reinterpreted.
+PRESS2="${PRESS2_DELAY:-16}"
+sleep "$PRESS2"
+echo "PRESS2 at ${SECONDS}s  (log frame marker below)"
+grep -c '^--- frame' "$OUT"/xenia_re_ui_draws_*.log | tail -1 | sed 's/^/frames at press2: /'
+pad "press=A"; sleep 0.4; pad ""
+sleep 90
+pkill -x xenia_canary
+echo "done at ${SECONDS}s"; ls -la "$OUT"/*.log 2>/dev/null