build: bend 2.0.34, ez follows it

[noah-emp]

Summary

• Pin bendlang/bend at 777ee0b, the commit whose flake packages Bend 2.0.34. The ez input follows that bend.
• The proof gate requires the first line of bend PROOF.bend to be ALL PROOFS CHECK.
• IO.args starts with the program name, so the bench reads the arguments after it.
• Proofs take the comparison with Pair.snd, where Base no longer defines String.eq.fin.

Test plan

• nix flake check

  

[noah-emp]

Superseded by #68. That PR keeps ez on its own Bend pin (2.0.31) until ez itself ships 2.0.34 — same pattern as ezaudio#40 — instead of inputs.bend.follows = "bend".