perf(encode): write scalars and scalar arrays without boxing

Assisted-by: GLM 5.3 Flash

CHANGELOG.md

@@ -188,6 +188,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 **Performance**
 
+- Marshal writes plain scalars and typed scalar arrays straight from their
+  reflect cells instead of boxing them into interface values first, and skips
+  the per-element resolution for arrays that can never take the `[[header]]`
+  form. The representative document now costs 130 allocations per call
+  instead of 141, the long array-of-tables document 55 915 instead of
+  63 660, with byte-identical output.
 - Parsing is faster than in 1.1.0 while carrying the new document layer:
   the suite's representative document decodes at about 79 MB/s with 104
   allocations per call, and the long array-of-tables document at about