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/wire/sample_usage.cpp

@@ -230,4 +230,4 @@ bool identityMatches(const std::string& identity, const std::string& uidHexUpper
     return !nameUpper.empty() && up.find(nameUpper) != std::string::npos;
 }
 
-}  // namespace reasampler::wire
+}  // namespace reasampler::wire