- Add a supports_mtp_export capability to ModelBase so architectures can opt
into --mtp and --no-mtp without extending a central class allowlist.
- Enable the capability for the existing Qwen3.5/3.6 and Step3.5/3.7
implementations, and for HY V3, whose converter already supports
filtering the appended MTP layers.
* move conversion code to a dedicated conversion directory and split the files akin to the src/models architecture
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Co-authored-by: Sigbjørn Skjæret <sigbjorn.skjaeret@scala.com>