port: P7 gate verified end to end, and a defect I nearly invented from a masked correlation

NEW GAME opens S00A, plays 93.33 s against the manifest's 93.9, returns to
title. Nine film frames distinct and non-black.

Nearly filed 'the movie's audio never reaches the bus' from r=-0.0068 at the
movie's known start, with the correlator passing its own control at r=1.0000.
False: re-run bed-free on the boot path, movie audio r=0.418 and voice r=0.886
at the same start. The menu bed masked the quieter movie below detection.

The lesson is the control: I validated the instrument on clean data and ran it
on masked data. A negative needs a positive control under the SAME masking.
Third unvalidated negative in this corpus to nearly become a finding.

Also confirms the Decoder's unresolvable-element hazard does not reach
GP_TITLE: 115 .t32, 45 .rat, 18 .prm, no .tbm, every non-primitive resolvable.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N7FiFFFwbvG2uxdcEh8HyF

docs/port/DECISIONS.md

@@ -5502,3 +5502,57 @@ additive, which is why those screens came out **solid black** rather than
 It is the reason the port can stop waiting on it. `pbafc.prm` remains the sole
 additive candidate and is outside the rule at 17×18 px; the port draws no
 additive quad either way.
+
+## P7 gate — the new-game intro plays and returns, and a defect I nearly invented
+
+`--menu=main_menu --script=accept` walks the P7 path: Ⓐ on NEW GAME announces the
+two measured screens this export skips, opens `S00A`, plays it to its natural end
+at **93.33 s** against the manifest's 93.9, and returns to the title. Nine film
+frames across the movie are distinct and non-black (mean 10 → 140). The gate asks
+for "plays, then returns to a defined state"; that is both halves.
+
+### The near-miss, which is the part worth keeping
+
+Checking that the movie's audio actually reached the Master bus, I correlated the
+recording against the exported `S00A.ogv` audio and got **r = −0.0068 at the
+movie's known start**, with the correlator passing its own positive control at
+**r = 1.0000**. A working instrument returning zero at the right place. I was one
+step from filing *"the movie's own audio never reaches the bus"* — which would
+have been a serious P4/P7 defect, and the inverse of the human's original report
+that the intro "plays music but no voice".
+
+It is false. Re-run on the **boot** path, where no menu bed is playing:
+
+| against the bed-free recording | r | at |
+|---|---|---|
+| `ADV` voice | **0.8855** | movie start 7.6 s |
+| `ADV` movie audio | **0.4178** | movie start 7.6 s |
+
+Both present, at the same start. The movie's audio is simply quieter than the
+voice mixed on top of it, and in the P7 run the **menu bed masked it below
+detection** while the louder voice survived. The bed carries across into the
+movie — `play_bed` is documented as carrying across submenus — so the P7 run was
+never a clean measurement.
+
+🔴 **The lesson is about the control, not the bed.** I validated the correlator on
+clean data and then ran it on masked data. A positive control proves the
+instrument works *on the material it was given*; it says nothing about whether
+the instrument can see through an interferer that was not in the control. **A
+negative result needs its own positive control under the same masking**, and this
+is the third time in this corpus that an unvalidated negative nearly became a
+finding — after "10 of 18 elements transparent at rest" and the burst counter that
+read 4 cues on one run and 0 on the next.
+
+`tools/port/verify-video-audio`'s header already warned that a fidelity
+comparison needs cross-correlation alignment *and* an agreed downmix. It was
+right, and I would add the third condition it did not know to state.
+
+⚠️ What is **not** settled: whether the bed *should* carry into the movie and on
+to the title after it. It does, it is authored that way, and nobody has watched
+the game do either. That is a separate question from this one and is not filed as
+a defect — only as unmeasured.
+
+✅ Also checked, from their `compose` finding: `GP_TITLE` declares **115 `.t32`,
+45 `.rat`, 18 `.prm` and no `.tbm` at all**, and every non-primitive element has a
+resolvable sprite. The "draws no pixels for an unresolvable element" hazard —
+the shape that hid `pteff05` from both renderers — does not reach this archive.