mtmd : add support for Voxtral (#14862)

* mtmd : add support for Voxtral

* clean up

* fix python requirements

* add [BEGIN_AUDIO] token

* also support Devstral conversion

* add docs and tests

* fix regression for ultravox

* minor coding style improvement

* correct project activation fn

* Apply suggestions from code review

Co-authored-by: Sigbjørn Skjæret <sigbjorn.skjaeret@scala.com>

---------

Co-authored-by: Sigbjørn Skjæret <sigbjorn.skjaeret@scala.com>

.gitignore

@@ -82,6 +82,7 @@ models/*
 models-mnt
 !models/.editorconfig
 !models/ggml-vocab-*.gguf*
+!models/templates
 
 # Zig
 zig-out/