Migrate Sortformer and Higgs Audio STT to spec v1

[0xShug0]

Summary

• migrate Sortformer diarization and Higgs Audio STT to schema-v1 model specs
• remove thin loader files and wire both models through the spec-backed loader path
• add compatibility aliases so old request/session option names are normalized before v1 validation
• update docs with the new option names and compatibility tables

Validation

• debug build: cmake --build build/debug -j 16 --target audiocpp_cli
• Sortformer: regenerated F16/Q8 GGUFs and compared old/new path-test outputs
• Higgs Audio STT: regenerated F16/Q8 GGUFs and compared old/new path-test text outputs
• verified migrated GGUF standalone loading from outside the repo-local model_specs directory