fix(nix): prevent stripping the Bun-compiled binary

[yutakobayashidev]

Prevent the Nix package from stripping the prebuilt ax binary.

The release binary is produced with bun build --compile. Nix's default strip phase removed Bun's embedded
application payload, leaving only the Bun runtime. As a result, the package built successfully, but running ax
launched the Bun CLI instead.

Changes

• Set dontStrip = true for the ax derivation
• Add an install check that verifies ax --version matches the packaged version

Verification

• nix build .#ax --no-link -L
• nix flake check -L
• Confirmed the packaged binary reports 0.1.20
• Confirmed ax --help displays the ax CLI help instead of the Bun CLI help

[yusukebe]

LGTM!

[yusukebe]

@yutakobayashidev

As a result, the package built successfully, but running ax launched the Bun CLI instead.

I didn't realize the behavior. Thanks!