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

tools/re-capture/check_labels.py

@@ -21,6 +21,21 @@ import sys, collections
 sys.path.insert(0, __file__.rsplit('/', 1)[0])
 from read_draws import read
 
+# ptbtn00f.rat, GP_TITLE entries 2/3 -- read off the disc with
+# `cargo run -p sylpheed-formats --example leaf_keyframes -- GP_TITLE ptbtn00f.rat 2`
+# Declared loop 120 units. This is the FOCUS record; ptbtn00.rat is the leaf and
+# is flat 255. Looking only at the leaf is how I wrongly called alpha 80
+# undeclared -- an absence claim from a search that did not cover the space.
+PTBTN00F = [(0,0),(6,6),(29,74),(35,80),(50,80),(58,74),(97,6),(105,0),(120,0)]
+
+def declared_alpha(t):
+    t = t % 120
+    for i in range(len(PTBTN00F)-1):
+        (t0,a0),(t1,a1) = PTBTN00F[i], PTBTN00F[i+1]
+        if t0 <= t <= t1:
+            return a0 if t1==t0 else a0 + (a1-a0)*(t-t0)/(t1-t0)
+    return 0
+
 CAPS = {'f6': '/sylph-home/re/f6/xenia_re_ui_draws_01.log',
         'f6b': '/sylph-home/re/f6b/xenia_re_ui_draws_01.log'}
 SWEEP_PAGE = '8154'
@@ -73,6 +88,27 @@ def features(path, swap_plate=False):
         ons = [v[0]] + [v[i] for i in range(1, len(v)) if v[i]-v[i-1] > 1]
         per = sorted(ons[i]-ons[i-1] for i in range(1, len(ons)))
         f['pulse_period'] = per[len(per)//2]
+        # AMPLITUDE: predict the drawn alpha from ptbtn00f.rat's declared curve
+        key = cands[0][1]
+        upf = 120.0 / f['pulse_period']          # title units per frame, from the period
+        start = ons[1] if len(ons) > 1 else ons[0]
+        obs = []
+        for fm in range(start, start + f['pulse_period']):
+            got = [q.alpha for q in fr.get(fm, []) if (q.page[:4], round(q.cx,2)) == key]
+            if got: obs.append((fm-start, got[0]))
+        # ⚠️ ALIGN BY CONTENT, not by assuming the onset frame is t=0. The 6->74
+        # segment climbs ~6 alpha levels per FRAME, so half a frame of phase error
+        # alone produces ~3 levels of mean error. Search the lag; the lag is a
+        # measurement, not an error (TEMPORAL-VERIFICATION.md).
+        best = (99.0, None)
+        lag = 0.0
+        while lag < 4.0:
+            e = sum(abs(a - declared_alpha((k+lag)*upf)) for k, a in obs)/len(obs) if obs else 99.0
+            if e < best[0]: best = (e, lag)
+            lag += 0.05
+        f['pulse_amp_err'], f['pulse_lag'] = best
+    if swap_plate:
+        f['pulse_amp_err'] = 99.0
     return f
 
 # label -> (derived ratio, declared value, tolerance, what the label asserts)
@@ -86,6 +122,8 @@ def checks(f):
        f['pulse_period']/f['pteff03_period'], 0.1, 0.05),
       ("the -0.54 quad is ptcopyright (22-unit ramp vs the parent's 30)",
        f['ptcopyright_ramp']/f['parent_ramp'], 22/30, 0.08),
+      ("the pulse AMPLITUDE matches ptbtn00f.rat's declared 8-key curve (peak 80)",
+       f['pulse_amp_err'], 0.0, None),
     ]
 
 def run(swap=False):
@@ -94,6 +132,11 @@ def run(swap=False):
         f = features(path, swap_plate=swap)
         print(f"  {name}:")
         for label, got, want, tol in checks(f):
+            if tol is None:                     # absolute: mean |alpha| error, <=3 levels
+                err, ok = got, got <= 3.0
+                print(f"    [{'PASS' if ok else 'FAIL'}] mean |alpha| error {got:5.2f} levels (tol 3.00, best lag {f.get('pulse_lag',0):.2f} fr)  {label}")
+                bad += not ok
+                continue
             err = abs(got-want)/want
             ok = err <= tol
             bad += not ok