Split cargo make task catalog

[yvette-carlisle]

Summary

• split the root cargo-make task catalog into focused makefiles/*.toml fragments
• keep the root Makefile.toml as the public cargo-make entrypoint via extend
• teach docs/tests to read the extended make task catalog
• exclude cargo-make fragments from taplo array sorting so command argument order remains stable

Validation

• RUSTC=/run/current-system/sw/bin/rustc cargo make check
• RUSTC=/run/current-system/sw/bin/rustc cargo make check-docs
• TOML task equivalence audit: old=129 new=129 changed=0
• line scan outside tmp/: no source/config files over 1000 lines