Stage 2: introduce `scout` command (review kept as hidden alias)

Rebrand the multi-agent command as entire scout, reusing the existing review engine. review stays as a hidden cobra alias for back-compat, so both invocations work. Updated command Use/Short/Long, user-facing guidance strings ("entire review …" → "entire scout …"), the labs entry, and affected test expectations.

Internal package, settings keys (review_profiles), and env vars (ENTIRE_REVIEW_*) are unchanged — branding only, no behavior change.