Q-W1 code-review follow-ups: restore 104 trailing newlines, relocate reasampler_uid.h to core/wire, drop ext_keys namespaces shim, add slot_map_tests, golden serialize literals for 4 modules, namespaces.h/pragma-once ordering sweep. 60/60 green.

src/core/instrument/ui/envelope_overlay.cpp

@@ -55,7 +55,6 @@ int levelToY(const Rect& area, double level) {
 
 namespace {
 
-
 EnvVertex vtx(EnvNode node, const Rect& area, double totalSeconds, double t, double level) {
     EnvVertex v;
     v.node = node;
@@ -172,4 +171,4 @@ std::vector<EnvVertex> buildEnvelopePolyline(const AmpEnvelope& env, const Rect&
                                      : triggerPolyline(env, area, totalSeconds);
 }
 
-}  // namespace reasampler::instrument::ui
+}  // namespace reasampler::instrument::ui