instrument: fix AHD node-tracking/tie-break/live-latch defects and close staged-envelope-curve test gaps

src/core/instrument/map/params_payload.cpp

@@ -14,15 +14,13 @@
 namespace reasampler::instrument::map {
 
 using reasampler::wire::ByteReader;
+using reasampler::wire::asU64;
 using reasampler::wire::bitsToDouble;
 using reasampler::wire::doubleToBits;
 using reasampler::wire::putLE;
 
 namespace {
 
-// Signed 64-bit values ride the wire as their two's-complement unsigned image.
-std::uint64_t asU64(std::int64_t v) { return static_cast<std::uint64_t>(v); }
-
 // Emit the OVERRIDE trio shared by the v2..v7 per-zone record and the v8 single record, so
 // the two shapes cannot drift byte-for-byte.
 void putOverrides(std::vector<std::uint8_t>& out, const InstrumentParams& p) {
@@ -149,8 +147,14 @@ double readCurveExponent(ByteReader& r) {
 }
 
 void readAhd(ByteReader& r, AhdSeconds& a) {
-    a.attackSeconds = bitsToDouble(r.u64());
-    a.decaySeconds  = bitsToDouble(r.u64());
+    // attackSeconds/decaySeconds reach resolvePlay's static_cast<std::int64_t> (sample_map.cpp)
+    // unguarded — UB on NaN, and on a large-enough finite value — so a corrupt/non-finite wire
+    // value degrades to 0 seconds rather than reaching that cast, the same guard readSecondsPlayTail
+    // and the v9 filter tail already apply to their own wall-clock fields.
+    const double attack = bitsToDouble(r.u64());
+    const double decay  = bitsToDouble(r.u64());
+    a.attackSeconds = std::isfinite(attack) ? attack : 0.0;
+    a.decaySeconds  = std::isfinite(decay) ? decay : 0.0;
     const double frac = bitsToDouble(r.u64());
     a.holdFraction  = std::isfinite(frac) ? frac : 0.0;
     a.attackCurve   = readCurveExponent(r);