port: H3 re-asked -- the plate is ON TIME, and it never blinks

PLAYTEST-2026-09-02 asks for this re-ask by name, and the previous plate numbers
were taken through the pose_at bug -- the same accident that manufactured H2's
false green.

Filmed a real boot and isolated the plate with its own sprite's transparent
holes: same rect, same rows, interleaved at pixel scale, so the moving title
sweep cancels. Two earlier isolations failed first and are recorded -- a rect
that overlapped the developer splash, and a control band 55px away that could
not cancel a sweep that MOVES.

Onset: flat through ou=213.9, risen by 222.1, declared t=214 inside the bracket;
88% of lit by t=238 against declared full at 236. NOT late.

But over 8.1 declared cycles (ou 6..1974) it never returns within 88% of dark,
where the disc declares 0 from t=244. rest.t=236 is the PULSE PEAK and holding
parks it there -- the exact family plate-arrival-halves.md named for transients
and nobody had checked on the plate itself.

Proposed, not changed: whether the guest pulses the plate is the Decoder's.

docs/port/plate-arrives-on-time-but-never-blinks.md

@@ -0,0 +1,120 @@
+# H3 re-asked after the animation fix: the plate is **on time**, and it **never blinks**
+
+**Status:** ✅ **the "arrives late" observation does not reproduce as a timing
+error** — measured on the current build, and the plate's onset sits on its
+declared keyframe. 🔴 **A different divergence in the same element is real and
+was not being looked for: the port holds `PRESS Ⓐ` lit permanently, where the
+disc declares a 30-unit pulse.** Written 2026-09-02 by the Port at `6263686`.
+
+`PLAYTEST-2026-09-02.md` asks for exactly this, in its own words: *"Worth
+re-asking now: the animation fix changed what the whole boot looks like, so the
+original observation may simply no longer reproduce."* And there is a specific
+reason to re-ask rather than assume — **the previous plate numbers were taken
+through the `pose_at` bug**, the same way the 0.01 % that manufactured H2's false
+green was.
+
+## What the disc declares
+
+`export/screens/title/press_start.json`, one element `ptbtn00`:
+
+```
+0:0   214:0   236:255   238:255   244:0        rest [383,550], sprite 513x50
+```
+
+Invisible until **214**, full at **236–238**, **gone by 244**. A 30-unit pulse.
+
+## The instrument, and the two controls it went through first
+
+Filmed a real boot (`--skip-at=1 --linger=8 --film-interval=0.05`), no `--time`,
+no pinning. Then **two attempts at isolating the plate failed before one worked**,
+which is the part worth keeping:
+
+1. 🔴 **A rect around the plate.** Contaminated — the rect overlaps the developer
+   splash earlier in the boot, so the onset detector fired on the wrong screen.
+2. 🔴 **A control band 55 px above the plate.** Still wrong. The title's
+   background sweep **moves**, so a spatially displaced control samples it at a
+   different phase and cannot cancel it. It showed a "rise" that was the sweep.
+3. ✅ **The plate sprite's own transparent holes.** Same rectangle, same rows,
+   interleaved with the glyphs at pixel scale — 7 672 glyph pixels against 10 412
+   hole pixels, both built from the sprite's alpha channel. A co-located
+   background sample, so `glyph − hole` is the plate and nothing else.
+
+⚠️ Control 2 is the same defect as everything else on this project: **an
+instrument that cannot see the thing it is measuring separately from the thing
+it is measuring against.** It produced a plausible curve. The tell was that the
+"plate" and the background rose together in phase.
+
+## Result 1 — the arrival is correct
+
+`glyph − hole`, dark baseline **0.003**:
+
+| overlay units | 205 | **214** | **222** | 230 | **238** | 246 |
+|---|---|---|---|---|---|---|
+| plate | 0.005 | **0.005** | **0.222** | 0.434 | **0.586** | 0.601 |
+
+**Flat through 213.9 and risen by 222.1.** The declared onset `t=214` sits inside
+that bracket, and the bracket is 8 units wide because that is the film's sampling
+interval, not a measurement of anything. By `t=238` the plate is at 88 % of its
+lit level, against a declared full alpha at 236.
+
+**The plate is not late.** Whatever the human saw in the 2026-09-01 play-test,
+the port's own clock puts `ptbtn00` on its declared keyframe.
+
+## Result 2 — 🔴 and it then stays lit forever
+
+The declared ramp returns to **0 at t=244**. It does not:
+
+| | |
+|---|---|
+| dark baseline, `t < 214` | **0.003** |
+| minimum at any point after `t = 250` | **0.587** (at `ou` 342) |
+| maximum after `t = 250` | **0.664** |
+| span measured | `ou` 6 → **1974** — **8.1 declared cycles** |
+
+Over eight cycles of its own declared timeline the plate **never returns within
+88 % of dark**. The 11.6 % ripple that is there is *not* the plate: it is in
+phase with the hole channel, i.e. it is the title's background sweep leaking
+through the anti-aliased glyph edges.
+
+### Why, and it is a failure mode this port already wrote down
+
+`ptbtn00`'s `rest.t = 236` and its settle instant is `t=236` — **the peak of the
+pulse**. `holding` parks the element there, so the port shows a `PRESS Ⓐ` plate
+that lights once and stays on.
+
+`plate-arrival-halves.md` names this exact class already, about a different
+element:
+
+> *"It is still wrong for transients — `ptlogo_back2eff1` is a two-frame flash
+> (0 at t52, `0xff` at t54–56, 0 by t58) and its `rest.t = 54` is the flash
+> **peak**, so `rest()` leaves five of these burning at once."*
+
+**The plate is an instance of the family that page predicted, and nobody had
+checked the plate itself** — because that page was written to *eliminate* `rest.t`
+as a cause of lateness, which it correctly did, and having eliminated it as the
+cause of *one* defect nobody asked what else it was doing.
+
+## What I have NOT changed, and why
+
+Nothing. The port still holds the plate.
+
+Reading the disc's keyframes is mine; **whether the running game pulses its
+`PRESS Ⓐ` plate is not.** The keyframes describe a blink and blinking is what
+`PRESS START` prompts conventionally do, but "conventionally" is not evidence and
+this project has been burned by exactly that kind of inference. The change is
+**proposed, not made**, and the Decoder has been asked for the one fact that
+settles it: does the plate pulse in the guest, and with what period?
+
+⚠️ **This is not a regression from the animation fix.** Before the fix `pose_at`
+*assigned* the settle instant, which parks the plate at `t=236` too. The plate
+has been held for as long as the port has drawn it; the fix neither caused this
+nor was supposed to.
+
+## What this does not claim
+
+* That finding 3 was wrong when it was made. It says the port measures on time
+  **now**, on a build whose boot the fix visibly changed.
+* That holding is wrong. It says the port's picture and the disc's keyframes
+  disagree, and names who can adjudicate.
+* Anything about the plate's **absolute** alpha or position. Onset timing and
+  whether it extinguishes, only.