Default configuration triggers its own deprecation warning for build.bin

[willie]

Describe the bug
When running air init, the tool prints a warning: [warning] build.bin is deprecated; set build.entrypoint instead, even though this warning is triggered by the default settings produced by defaultConfig() in runner/config.go.

To Reproduce

• Run air init with no existing .air.toml in your repo.
• Observe the warning: [warning] build.bin is deprecated; set build.entrypoint instead.
• Inspect the code in defaultConfig() in runner/config.go, which sets Bin = "./tmp/main" and leaves Entrypoint empty by default.
• The warning logic in warnDeprecatedBin triggers when Bin is set and Entrypoint is empty.

func defaultConfig() Config {
    build := cfgBuild{
        Cmd:          "go build -o ./tmp/main .",
        Bin:          "./tmp/main",    // <--- Deprecated field is set
        Entrypoint:   entrypoint{},    // <--- This being empty satisfies the warning condition
        // ...
    }
    // ...
}

func warnDeprecatedBin(cfg *Config) {
    if cfg == nil {
        return
    }
    if cfg.Build.Bin == "" || len(cfg.Build.Entrypoint) > 0 {
        return
    }
    fmt.Fprintln(os.Stdout, "[warning] build.bin is deprecated; set build.entrypoint instead")
}

Expected behavior
air init should not warn users about deprecated configuration in its default configuration. The tool's own defaults should not violate its own recommended practices.

Desktop:

• OS: macOS 26.3
• Air Version: 1.64.5