DFTools v0.1.0

ci: temporarily decouple publishing from the DFHDL gate

Publish now depends only on build-test so freshly built images can be released
and used to iron out outstanding gate issues. The dfhdl-gate still runs for
visibility but no longer blocks publishing. Restore `needs: dfhdl-gate` once the
gate is green.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>