[GLD Serializer Benchmark] Rust flexbuffers 2.0.0 — spec compliance misses

Hi — this is a friendly report from the [GLD Serializer Benchmark](https://github.com/leo-gan/GLD.SerializerBenchmark), an independent multi-language suite that times serializers **and** checks them against the published format specs (RFC 8259, YAML 1.2, …).

We measured **flexbuffers 2.0.0** on **Rust**. The suite recorded spec-profile misses for this pin. The catalog is **report-only**: a miss is not a CI failure, and some cases are older or stricter profiles (for example RFC 4627 vs RFC 8259) rather than a crash.

## Compliance results (please start here)

This link opens the live heatmap on **Rust** with **flexbuffers** already selected (All standards). Click a scored cell for each FAIL and the cited spec paragraph:

https://leo-gan.github.io/GLD.SerializerBenchmark/dashboard/#compliance/rust/flexbuffers

How the catalog is built, and how to read a FAIL line:

- https://leo-gan.github.io/GLD.SerializerBenchmark/compliance/
- https://leo-gan.github.io/GLD.SerializerBenchmark/compliance/reading-results/

I am not pasting the case list here so you can use the Dashboard (filters, heatmap, and spec links) rather than a static dump.

Optional: one standard family only — `#compliance/rust/flexbuffers/json` (or `yaml`, `cbor`, …).

## Benchmark timings (same pin)

The same suite also publishes encode / decode time and payload size for this library on Rust:

https://leo-gan.github.io/GLD.SerializerBenchmark/dashboard/?lang=rust&data=document@n=1&mode=bytes#dashboard

Details table (this library pre-selected):

https://leo-gan.github.io/GLD.SerializerBenchmark/dashboard/?lang=rust&ser=flexbuffers&data=document@n=1&mode=bytes#detailed-analytics

That page is the live L1 snapshot, not a claim that one library is “best.”

## Ask

Please look at the Compliance view for **flexbuffers**. If a miss is a real decoder/encoder bug you want to fix, great. If it is an intentional default (accepting NaN, YAML 1.1 bools, …), a short note here is enough — we will keep the catalog as-is unless the library’s documented contract changes.

Thanks for the library.

Start with the Compliance view for Rust flexbuffers 2.0.0 and open each FAIL cell to read its cited specification paragraph; use the linked compliance and reading-results pages to understand the profiles. Determine whether each miss is a real encoder/decoder bug or an intentional default, then either identify the relevant behavior to fix or document the intentional contract here.

Written by the indexing model from the issue text.