re: RETRACT "the game never draws eff3" -- a batched draw merged two quads

The console draws all five title flashes. My claim that ptlogo_back2eff3 is
never drawn was an instrument artefact, and I had reported it to the port with
three alternative explanations "ruled out".

A GPU draw can batch several quads -- indices=4 is one, indices=8 two,
indices=24 six -- and the UI draw log dumps only the first 8 vertices. Taking
min/max over a line's whole vertex list merges quads into one box.

eff3 is batched with eff4, and because the wipe family is right-aligned, eff3
(788..1196) lies ENTIRELY INSIDE eff4 (447..1196). The union is exactly eff4's
own extent, so the merged box matched eff4 to 1 px, eff3 vanished, and nothing
looked wrong.

Parsed per quad, all five fire in both title entries in the declared stagger:
eff1 130-131, eff2 133, eff3 133-134, eff4 133-135, eff/eff5 134+, back2 136+;
and 5953-5955 / 5955-5957 / 5957-5958 / 5957-5959 / 5958+ / 5962+ in entry 2.
Frames 133 and 134 are t=60.1 and 62.3, inside eff3's declared t in (58,64).

Also retracts "the developer splash is one composited quad" -- the same bug,
which the port refuted by arithmetic first (a 259-tall box cannot contain three
logos spanning y 164..585). It draws three logos and three glows as separate
quads in one indices=24 call; the 525x259 was gamearts_eff merged with
seta_eff. The 9-unit black hold is unaffected: those glows are the developer
splash's first draw.

The three "ruled out" explanations were all aimed at the wrong failure. In
particular the invisible-draw check counted draws with NO geometry line, when
the hiding place was draws with PARTIAL geometry. Refuting three wrong
hypotheses is not evidence for a fourth, and a list of failure modes written by
whoever built the instrument is the least likely to contain its blind spot.
Recorded in METHOD.md, along with the tell that was present and explained away:
a merged box carries the first quad's colour, which made one element's alpha
read 255/127/254 on consecutive frames.

New tool: tools/re-capture/quads_per_frame.py parses vertices in groups of four
and warns when the logged quad count falls short of indices/4.

Also guards a double-A-tap in ui_draw_capture.sh: the movie branch ignored that
TARGET=menu had already tapped, so a run tapped A on the title at t=23s and
again at t=27s on the transition; the guest faulted and Xenia dumped registers
to stdout until the file reached 519 MB.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QsEPXWVaEpyfudtR6re1Pd

docs/re/METHOD.md

@@ -1080,3 +1080,44 @@ title binds only 1280×768 pages — both were there to be read first.
 
 The general shape: **a coincidence of size is not an identification.** Before
 matching on one attribute, ask what else in the frame shares it.
+
+## A batched draw merges quads, and the merge can be invisible
+
+A GPU draw can carry several quads — `indices=4` is one, `indices=8` two,
+`indices=24` six — and the UI draw log dumps **only the first 8 vertices**. Taking
+min/max over a log line's whole vertex list therefore silently *merges* quads into
+one bounding box.
+
+This produced two wrong findings in one session, one of them reported to another
+agent with three alternative explanations "ruled out":
+
+* **`ptlogo_back2eff3` "is never drawn by the game".** It is batched with
+  `ptlogo_back2eff4`, and because the wipe family is right-aligned, `eff3`
+  (788…1196) lies **entirely inside** `eff4` (447…1196). The union is *exactly*
+  `eff4`'s extent — so the merged box matched `eff4` to 1 px, `eff3` vanished, and
+  nothing looked wrong.
+* **"the developer splash is one composited quad."** `gamearts_eff` and
+  `seta_eff` merged into a box that was read as the bounding box of three logos —
+  which it could not have been, since it was 259 px tall and they span 421.
+
+**Why the checks failed.** Three hypotheses were tested and refuted — sampling
+phase, a draw with no geometry logged, a bad position guess. All three were aimed
+at the wrong failure. In particular the "invisible draw" check counted draws with
+**no** geometry line; the hiding place was draws with **partial** geometry, which
+was never looked for.
+
+> 🔴 **Refuting three wrong hypotheses is not evidence for a fourth.** The
+> confidence gained from "I ruled out everything I could think of" is worth
+> exactly as much as the list was complete, and a list of failure modes assembled
+> by the person who built the instrument is the least likely to contain that
+> instrument's own blind spot.
+
+Parse vertices in groups of four, one per quad, and **compare the logged quad
+count against `indices / 4`** — `tools/re-capture/quads_per_frame.py` does both and
+warns on the shortfall.
+
+⚠️ A related tell that was present and ignored: a merged box carries the *first*
+quad's vertex colour, which made one element's alpha read 255 / 127 / 254 on
+consecutive frames. That non-monotonicity was noticed, written down as "the
+vertex-alpha identity does not generalise", and not chased. **An anomaly you
+explain away is cheaper to chase than to re-derive later.**