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.h

@@ -250,4 +250,4 @@ bool identityMatches(const std::string& identity, const std::string& uidHexUpper
 // ASCII-only uppercase (shared by the matcher and the shell's needle preparation).
 std::string toUpperAscii(const std::string& s);
 
-}  // namespace reasampler::wire
+}  // namespace reasampler::wire