Γ-W1-T5 remediation: narrow the rate-bound claim, fix baseline/measurement provenance, correct §2.4 framing

Re-derives the splice-cadence inequality and adds a corner probe that FAILS at
P=500 by design, pending a ruling. Names the baseline commit and harness edit,
fixes measurement methodology, corrects the Trigger-AHD/rate coupling framing.

src/core/instrument/engine/voice.cpp

@@ -327,6 +327,8 @@ void Voice::retune(int note) {
     // Filter key-tracking follows the pitch: it is a function of the note, so a slide moves it
     // too. The velocity offset deliberately stays the first note's, matching velocityGain_.
     if (filterOn_) updateFilterCutoffBase(note);
+    // stretchRate_ (Preserve's duration control) is untouched here too — it is a note-on latch
+    // like velocityGain_, not a per-note property to re-resolve on a legato slide.
 }
 
 void Voice::release() {