re: RETRACT the alpha-80 refutation -- it is declared, in ptbtn00f.rat

I claimed ptbtn00f's peak alpha of 80 was capture-only and refuted the
port's audit with it. Verified on the disc myself: ptbtn00f.rat, loop 120,
eight keyframes 0:0 6:6 29:74 35:80 50:80 58:74 97:6 105:0. ptbtn00 carries
TWO child records -- the leaf ptbtn00.rat (flat 255, which I read and
described correctly) and the focus record ptbtn00f.rat, which holds the
pulse. My "nothing declares 80" said only that nothing reached my
enumeration. METHOD.md has five entries on exactly this class.

Resolves the 🟡 with it: the corpus line attributing the 120-unit loop to
ptbtn00f is correct as written.

Turns the retraction into a stronger check. The amplitude is declared, so
check_labels.py now verifies the SHAPE: mean |alpha| error 1.14 levels (f6)
and 0.35 (f6b) against the declared 8-key curve. The first version assumed
the onset frame was t=0 and f6b FAILED at 3.24; the fix was aligning by
content rather than loosening the tolerance, since the 6->74 segment climbs
~6 levels per frame. Best lag is ~1 frame in both runs -- the element is not
drawn while its curve sits at alpha 0.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Jc4pciRArGHfxGGhEbwp5t

docs/re/label-check-and-the-alpha-80-refutation.md

@@ -42,36 +42,51 @@ OK: mislabel detected (2 failures)
 82–83 % against a 5 % tolerance, and the other three still pass, so the failure
 is localised rather than a global break.
 
-## 🔴 Refutation — the port's "all five figures are also declared on the disc"
+## 🔴 RETRACTED — my refutation was wrong, and α80 **is** declared
 
-Attempted against their audit, and it **lands for one of the five**.
+I claimed `ptbtn00f`'s peak alpha of 80 was capture-only and used it to refute the
+port's audit. **Wrong.** Verified on the disc myself with
+`examples/leaf_keyframes.rs`:
 
-`ptbtn00f`'s **peak alpha of 80** is a figure I measured and sent them. The disc
-does not declare it:
+```
+GP_TITLE entry 2 — ptbtn00f.rat (leaf 424 bytes), declared loop 120 units
+  ptbtn00f.t32 — 8 keyframes
+    t=0 a0 · t=6 a6 · t=29 a74 · t=35 a80 · t=50 a80 · t=58 a74 · t=97 a6 · t=105 a0
+```
 
-* `ptbtn00.rat` **parent** (`GP_TITLE` entries 2 and 3): `t=0 α0 · 214 α0 ·
-  236 α255 · 238 α255 · 244 α0`;
-* its **leaf**: declared loop **120 units**, one keyframe, **α255 flat**.
+**`ptbtn00` carries two child records and I read one.** `ptbtn00.rat` is the
+*leaf* — flat α255, which is what I found and described correctly. `ptbtn00f.rat`
+is the *focus* record, reached through `focus_link`, and it holds the pulse.
 
-**Nothing declares 80, and nothing in the declaration pulses at all.** The
-*period* is declared and checks out; the *amplitude* is capture-only. So that
-figure cannot be arbitrated by their check, and "all five declared" is wrong for
-it — which matters because a check reporting PASS over a value it cannot see is
-the failure mode their own note warns about.
+**This is an absence claim from a search that did not cover the space.** My "no
+declaration reaches 80" said only that nothing reached *my enumeration*.
+`METHOD.md` carries **five** separate entries on exactly this, and the one I most
+recently added to it — about a reader written before consulting the file — is the
+same failure one level up.
 
-## 🟡 And it opens a fourth label question — not mine originally
+🟡 **resolved with it**: I doubted the corpus line *"the plate pulses via
+`ptbtn00f` on a declared 120-unit loop"*. It is correct as written. `ptbtn00f` is
+in the record because it **is** the record.
 
-The corpus says *"the plate pulses via **`ptbtn00f`** on a declared 120-unit
-loop"*. The 120-unit loop belongs to **`ptbtn00.rat`**, whose leaf contains
-**`ptbtn00.t32`** — there is no `ptbtn00f` in it. `ptbtn00f` is a real element
-elsewhere (the blend page has it at `0x0112`, additive), but the thing carrying
-the declared 120-unit loop is not obviously it.
+## ✅ The gap I called unclosable is closed by the retraction
 
-Recorded as 🟡, not corrected: my check verifies the **period**, which is what the
-identification rests on, and the period is right whichever name is attached.
+Because the amplitude is declared, it is checkable — so `check_labels.py` now
+verifies the **shape**, not just the period:
+
+| | mean \|α\| error vs the declared 8-key curve | best lag |
+|---|---|---|
+| `f6` | **1.14** levels | 0.90 frames |
+| `f6b` | **0.35** levels | 1.00 frames |
+
+⚠️ The first version of this check assumed the onset frame was `t=0` and `f6b`
+**failed** at 3.24 levels. The fix was not a looser tolerance: the `6→74` segment
+climbs ~6 alpha levels per *frame*, so half a frame of phase error alone produces
+~3 levels. Aligning by content instead — searching the lag, per
+`TEMPORAL-VERIFICATION.md` — gives the table above. **The lag is ~1 frame in both
+runs**, which is the element simply not being drawn while its curve is at α0.
 
 ## Reach
 
-The check covers labels made by matching a declared quantity. A label with no
-declared counterpart — the leaf **rate**, and now this **α80** — is still
-unchecked, on my side as on theirs.
+The check covers labels made by matching a declared quantity. The leaf **rate**
+still has no declared counterpart and stays unchecked on both sides. **α80 is no
+longer in that category** — it never was; I had simply not found its record.