re: the sweep IS drawn on the JP title -- and my gate was phase-locking the shutter

The occlusion hypothesis is refuted: build 7 draws the same three ROT strips at
higher alpha than English, so there was never an absence to explain.

The 0.32-vs-11.9 tension that motivated it was an artefact of my own instrument.
Both JP captures were shuttered on the plate pulse, and the plate's pulse is part
of the animation -- so the gate synchronises the shutter to the animation's phase.
Measured at the shutter instant, the sweep sits 25-26 px apart across two runs in
different locales and different sessions: 1.6 % of a ~1600 px traverse.

So the 0.32 I recorded as between-session capture noise measures my trigger's
repeatability, and I read it as evidence the title is still when it is evidence
the gate works. The era adjudication is unaffected -- margin 16.72 clears even the
un-locked 11.9 -- and unaffected for the reason that file already gave: correlated
noise cancels in a margin.

Refutation attempt on sylpheed-port's positional-mechanism rejection: FAILED, the
claim stands. Its residual sits inside lit logos, and the logo ROI is
byte-identical across five differently-phased frames in two sessions.

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

docs/re/structures/plate-pulse-phase-lock.md

@@ -0,0 +1,70 @@
+# The plate-pulse gate phase-locks the shutter to the title animation
+
+**measured** — 2026-08-30 · [data](../data/title-sweep-jp-draw-capture.txt) ·
+instrument `tools/re-capture/jp_draw_capture.sh`, control the English title
+draw log
+
+## The claim
+
+`wait_plate_pulse.py` waits for the title plate's glyph count to sit in
+[500, 2500] for 12 samples, and every title capture in this corpus shutters on
+it. It was adopted to answer *"has the screen settled?"* — and it does.
+
+But the plate's pulse **is** part of the title's animation, so gating on it does
+not only wait for settling: it **synchronises the shutter to the animation's
+phase**. Two runs gated this way are not two samples of a free-running clock.
+
+## The measurement
+
+The x of each tall ROT strip at the **first captured frame** — the shutter
+instant — in two independent runs, different sessions, *different locales*:
+
+| strip | EN run | JP run | apart |
+|---|---|---|---|
+| 883×1134 | x = −109 | x = −83 | **26 px** |
+| 1299×1303 | x = 486 | x = 461 | **25 px** |
+
+Against a traverse of ~1600 px, that is **1.6 %**. Two boots, two locales, two
+sessions, and the sweep is in essentially the same place both times.
+
+## What it invalidates — my own reading
+
+[`jp-title-at-rest.txt`](../data/jp-title-at-rest.txt) reasons that its second
+capture probes a new axis, *"BETWEEN runs, where a free-running clock lands
+somewhere else on a fresh boot"*, and reports **RMSE 0.32** in the era box as
+the between-session **capture noise**.
+
+🔴 **The clock does not land somewhere else.** The gate puts it back in the same
+place. So:
+
+* **0.32 is a phase-locked LOWER BOUND on capture noise, not capture noise.**
+  At an arbitrary phase the in-box figure is the **11.9** measured between two
+  EN captures a plateau-phase apart. Anything reusing 0.32 as "the noise floor"
+  is quoting the gate, not the game.
+* I read the 0.32 as evidence the JP title is **still**. It is not. It is
+  evidence the **gate works**. I had it backwards.
+* The whole-frame 116 492 px that *do* differ between those two sessions are
+  consistent with exactly this: ~25 px of residual jitter displacing two large
+  bright diagonal strips moves a lot of pixels globally while barely clipping
+  the era box.
+
+## What it does NOT invalidate
+
+✅ **The era adjudication stands.** Its margin is **16.72** (41.69 fixed vs
+58.41 stale), which exceeds even the un-locked **11.9** figure — so it survives
+whichever noise number is correct. And the file's own key insight is untouched
+and is the reason it survives: capture noise moves both candidates together and
+**nearly cancels in a margin** (absolute scores moved 0.001–0.002 between
+sessions; the margin moved 0.001).
+
+✅ **The within-run at-rest result stands** — five frames ~1.5 s apart are *not*
+gated individually, so they sample different phases, and the logo ROI is
+byte-identical across them in **both** sessions while 5–8 % of the frame moves.
+
+## Reach of the negative
+
+This says the gate locks phase; it does not say by what mechanism. Both runs
+boot the same ISO from the same state, so the pulse may simply occur at a fixed
+offset from a deterministic boot rather than the gate doing the locking. **Two
+runs deliberately shuttered at different phases would separate those** and were
+not run.