re: a third title->menu replicate, from a run that ran the wrong experiment

Set out to measure menu -> EXTRAS, the reverse of the pair measured at a 2-frame
gap, to test whether the black gap is a property of the screen pair or of the
direction. The run did not do that.

A three-part patch to fade_decompose.sh asserted two of its three replacements
and left the third -- the branch condition -- unchecked. It silently failed, so
WHERE=menu2extras fell through to the `title` branch. The capture is well-formed
and is of a different transition than intended, which is the build-ordinal error's
shape again: right-looking output for the wrong object. What caught it was the log
LACKING the navigation lines the intended branch prints; the data itself looked
entirely fine.

Salvaged, because the accidental transition is one already measured twice:

  run   outgoing ramp             black   incoming decay
  1     67-70: 63,127,191,255     3       73-77
  2     64-67: 63,127,191,255     3       70-74
  3     92-95: 63,127,191,255     3       98-103

Three independent runs, gap = 3 frames every time, outgoing ramp byte-identical
in all three. That takes "the black gap is not a load" from two replicates to
three, and makes the 4-frame outgoing ramp as solid as anything measured here.

menu -> EXTRAS remains open; the condition is fixed (with an assertion this time)
and the run has not been taken.

METHOD gains two entries. Assert every edit, not most of them -- and have each
branch announce itself in the log, so a run that took the wrong path says so
before its numbers are read. And: "appears nowhere in crates/" is a claim about a
TREE. sylpheed-port found SYLPHEED_KF_TIME_SHIFT live at ui_layout.rs:497 on their
branch, which carries the stale era; both statements are true of different trees.
With main 145 commits behind and each agent on a topic branch, any claim about
what the code contains needs its ref attached.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Wuu56cE8vJGTBtn1ppsk8v

tools/re-capture/fade_decompose.sh

@@ -24,6 +24,10 @@
 # WHERE=menu (default) arms on the main menu and presses (B)  -> menu -> title.
 # WHERE=title            arms on the boot title and presses (A) -> title -> menu.
 # WHERE=extras           navigates to EXTRAS, arms there, presses (B) -> menu.
+# WHERE=menu2extras      navigates to EXTRAS, (B)s back to the menu with focus
+#                        restored, arms there and presses (A) -> EXTRAS. The
+#                        REVERSE pair, to test whether the black gap is a property
+#                        of the screen pair or of the direction.
 #                        Tests whether "(B) has no black interval" is a rule or
 #                        one screen pair -- sylpheed-port's BLOCKED.md ask #1.
 # The two transitions have DIFFERENT declared fade-ins for the incoming screen --
@@ -71,7 +75,7 @@ if [ "$WHERE" = "menu" ]; then
   done
   [ "$s" = "menu" ] || { echo "NO MENU (screen=$s)"; exit 2; }
   BTN=B
-elif [ "$WHERE" = "extras" ]; then
+elif [ "$WHERE" = "extras" ] || [ "$WHERE" = "menu2extras" ]; then
   python3 "$SD/pad.py" tap A 0.5
   for _ in 1 2 3 4 5 6; do
     sleep 4; s="$(screen)"; echo "  after A: $s"
@@ -90,12 +94,31 @@ elif [ "$WHERE" = "extras" ]; then
     shot "$OUT/try$try.png"
     w="$(python3 "$SD/which_title_screen.py" "$OUT/try$try.png")"
     echo "  try $try: $w"
-    case "$w" in extras*) found=1; break;; esac
+    # ⚠️ REQUIRE A MARGIN. The first version accepted any line starting
+    # "extras", but which_title_screen.py returns a nearest-match even for a
+    # screen outside GP_TITLE entirely -- where the margin collapses to ~0.1.
+    # A bare prefix test would then accept a wrong screen on a coin flip. The
+    # control puts a true match at ~10-11; require > 5.
+    m=$(echo "$w" | sed -n 's/.*margin \([0-9.]*\).*/\1/p')
+    ok=$(awk -v m="${m:-0}" 'BEGIN{print (m>5)?1:0}')
+    case "$w" in extras*) [ "$ok" = 1 ] && { found=1; break; }
+                          echo "    (rejected: margin ${m:-?} <= 5)";; esac
     python3 "$SD/pad.py" tap B 0.5; sleep 5
     python3 "$SD/pad.py" dpad UP 0.3; sleep 2
   done
   [ -n "$found" ] || { echo "NEVER REACHED EXTRAS"; exit 3; }
-  BTN=B
+  if [ "$WHERE" = "menu2extras" ]; then
+    # We are ON extras. (B) returns to the menu with focus RESTORED on EXTRAS
+    # (measured 4/4, menu-navigation-semantics.md), so arming there and pressing
+    # (A) gives the menu -> EXTRAS transition: the exact reverse of the pair
+    # already measured at a 2-frame gap.
+    python3 "$SD/pad.py" tap B 0.5; sleep 6
+    shot "$OUT/back-on-menu.png"
+    echo "  back on menu: $(python3 "$SD/which_title_screen.py" "$OUT/back-on-menu.png")"
+    BTN=A
+  else
+    BTN=B
+  fi
 else
   # arm on the title itself and press (A): the incoming screen is then build 5,
   # whose declared fade-in is 12 units where build 4's is 16.