Raw compare. .NET Unicode categories for L/N, an embedded Default_Ignorable range table (Unicode 16.0).
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Pins Heimdall's rule: a write_admitted messageId needs a Unicode letter or number and no
Default_Ignorable_Code_Point, compared raw. Shared vectors plus a runner test in TS, Python,
Kotlin, C# and Rust. No decoder changed; the refuse vectors fail.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>