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

src/core/instrument/map/CMakeLists.txt

@@ -21,7 +21,7 @@ reasampler_test(bank_sync LINK bank_sync)
 # the format already keeps on independent version axes (see component_state_io.h).
 reasampler_pure_library(component_state_io
     SOURCES component_state_io.cpp params_payload.cpp
-    LINK PUBLIC velocity_curve master_gain)
+    LINK PUBLIC velocity_curve master_gain curve_law)
 # Links only component_state_io, deliberately no sampler_core/pitch_shift: the structural
 # proof the codec is engine-free, which is what keeps engine object code out of the extension.
 reasampler_test(component_state_io LINK component_state_io)
@@ -29,7 +29,7 @@ reasampler_test(component_state_io LINK component_state_io)
 # The mapping's product is plain SampleData, so the voice engine is not a dependency.
 reasampler_pure_library(sample_map
     SOURCES sample_map.cpp
-    LINK PUBLIC bank_book wav_codec velocity_curve peaks)
+    LINK PUBLIC bank_book wav_codec velocity_curve peaks curve_law)
 # Links only sample_map + component_state_io: the same plain-data-boundary proof, spanning
 # both halves of the mapping/codec split where the frozen-format assertions live.
 reasampler_test(sample_map LINK sample_map component_state_io)

src/core/instrument/map/component_state_io.cpp

@@ -17,15 +17,13 @@ namespace reasampler::instrument::map {
 
 using engine::masterGainMaxLinear;
 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); }
-
 // Apply a payload read to the state: the adoption rule (a retired payload's first zone
 // supersedes the envelope's selection id) lives here, once.
 void applyPayload(ComponentState& out, PayloadRead read) {

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);

src/core/instrument/map/sample_map.cpp

@@ -203,8 +203,8 @@ DecodedPcm decodeChannels(const std::vector<AudioSample>& interleaved,
 }
 
 PlayParams resolvePlay(const PlaySeconds& stored, int sampleRate) {
-    // seconds -> frames at the LIVE rate; source-timeline quantities (trigger %-length +
-    // fades) carry through untouched, already frames/fractions.
+    // seconds -> frames at the LIVE rate; the source-timeline quantity (trigger %-length)
+    // carries through untouched, already a fraction.
     assert(sampleRate > 0 && "resolvePlay: sampleRate must be > 0 (programming error)");
     const double sr = sampleRate > 0 ? static_cast<double>(sampleRate) : 1.0;  // 1.0 avoids div-by-zero; assert fires first
     const auto secToFrames = [sr](double sec) {