[FEATURE] improve error message for missing auth for ADO repo

[markheath]

When installing packages from an Azure DevOps repo without an Azure DevOps PAT configured, apm install fails with a generic “Failed to clone repository” error. The failure gives no indication that authentication is missing, which makes diagnosis non‑obvious for first‑time users.

Example anonymized output:

[*] Validating 1 package...
[+] dev.azure.com/<org>/<project>/<repo>/<path>#main
[*] Updated apm.yml with 1 new package(s)
[>] Installing 1 new package...

-- Diagnostics --
  [x] 1 package failed:
    +- <package-name> -- Failed to download dependency <org>/<project>/<repo>: Failed to clone
repository: C:\Users\<user>\AppData\Local\Temp\tmpxxxxxx\repo_clone

[x] Installation failed with 1 error(s).

Proposed behaviour:

APM should detect that:

• The dependency host is dev.azure.com, and
• No ADO_APM_PAT is configured

…and emit a more actionable error, for example:

Azure DevOps authentication required.
Set the ADO_APM_PAT environment variable with a PAT that has Code (Read) scope.

[sergio-sisternes-epam]

Thanks for reporting this, @markheath — the current "Failed to clone repository" error is definitely unhelpful for ADO users.

Triage summary:

• Confirmed: when the dependency host is dev.azure.com and no ADO_APM_PAT is set, APM should detect the missing auth and emit an actionable error pointing to the env var.
• This is a focused UX improvement with a clear scope — good candidate for a first contribution.

Accepting as enhancement / accepted / good first issue.