feature: compiled-binary e2e smoke

[atkrad]

What problem would this solve?

v1 e2e (#37) drives Deployah in-process via nabattest.Run. That catches most command wiring, but not argv/exec packaging issues: real process exit codes, signal handling, or a broken release binary/nix run entrypoint.

What do you want?

A small compiled-binary smoke (separate from or beside #37):

• Build deployah once (CI artifact or nix build).
• Exec a few non-cluster checks: version / --help, known exit codes.
• Optionally one short cluster command if cost stays acceptable.
• Keep this thinner than the full Kind deploy smoke; do not replace proposal: Kind-based e2e layer (cluster lifecycle + deploy smoke) #37.

Depends on: #37 (or can land in parallel if scoped to non-cluster checks only).

Alternatives considered

• Rely only on nabattest forever — misses binary packaging.
• Replace nabattest e2e with binary-only — slower and harder to capture structured IO for v1.