fix: fail Makefile smoke tests on npm packaging errors

[TYH71]

Problem

make npm-package-test can pass even when npm packaging commands fail.

Observed locally:

• npm pack --dry-run failed with npm cache EPERM
• make npm-package-test still exited 0

Cause: the Makefile recipe runs multiple commands in one shell block without set -e, so a failed middle command can be masked by the final successful rm -rf.

Same risk exists in the install smoke block under make test.

Impact: CI can pass while packaging/install smoke checks are broken.

Proposed solution

• Add set -e; at the start of the multi-command recipe blocks.
• Use a temp npm cache for npm pack --dry-run, matching npm install behavior.
• Ensure temp dirs are still cleaned up on success.

Alternatives considered

• Split each smoke command into separate Makefile recipe lines.
• Wrap smoke logic in a dedicated shell test script with set -euo pipefail.
• Use trap cleanup for stronger temp-dir cleanup if moving logic into a script.

Scope

• This does not require reading, copying, printing, uploading, or rewriting Codex auth tokens.