Dead code: unreachable fallback path in RepoRelease.downloadChart

[zacharyblasczyk]

Description

In pkg/wandb/spec/charts/repo.go:278-281, the fallback destination path can never trigger:

dest := filepath.Join(os.Getenv("HELM_DATA_HOME"), "charts")
if dest == "" {
    dest = "./charts"
}

When HELM_DATA_HOME is empty, filepath.Join("", "charts") returns "charts" (not ""), so the dest == "" guard is never true and the "./charts" fallback is dead code.

Functionally benign since "charts" and "./charts" resolve to the same path, but the dead branch is misleading.

Suggested fix

Either remove the dead branch or check the env var directly:

dest := os.Getenv("HELM_DATA_HOME")
if dest == "" {
    dest = "./charts"
} else {
    dest = filepath.Join(dest, "charts")
}

Found during review of #147.