Close two defeatable ReleaseProof guards and fix the static-lane skip's dead comparison

ReleaseProof{} and copy-reuse both compiled under this project's C++17;
user-provided ctor, deleted copy ctor and friend close them. The skip now
compares stored values, not norms, so it actually fires. Abort downgraded
to a debug assert.

src/core/instrument/engine/live_params.h

@@ -70,11 +70,13 @@ struct LiveValues {
 // The seqlock copies the block as raw bytes, which is only defensible for a plain value type.
 static_assert(std::is_trivially_copyable_v<LiveValues>,
               "the live block is copied under a seqlock — it must stay a plain value");
-// Guards operator== against silent staleness: a member added to the struct above changes this
-// size, so the assert fails at the new member's own commit instead of leaving a live control
-// that never reaches a sounding voice with no compiler or test signal. Confirmed 352 bytes,
-// MSVC 19.44 x64, Release (`SizeProbe<sizeof(LiveValues)>`, an incomplete-template size probe
-// whose error message reports the value). Bump the literal AND operator== together.
+// A SIZE-CHANGING edit only: padding can absorb a member added beside an existing one (a bool
+// beside splineActive, a fifth FilterSettings float) without moving this literal at all, so this
+// assert is NOT the guard against a forgotten operator== field —
+// testEveryFieldOfLiveValuesIsCompared (test_live_params.cpp) is that guard, poisoning one leaf
+// at a time. This assert only catches an edit that changes sizeof(LiveValues) itself. Confirmed
+// 352 bytes, MSVC 19.44 x64, Release (`SizeProbe<sizeof(LiveValues)>`, an incomplete-template
+// size probe whose error message reports the value). Bump the literal AND operator== together.
 static_assert(sizeof(LiveValues) == 352,
               "a member was added or removed — extend operator== in live_params.cpp to match");