pick_for_city gains a scout branch (after the early-military floor, before
expansion): when dwarf_scout is buildable (its tech/race/resource/building gates
met — mirrors pick_best_unit_of_type) and the capital owns no scout, the capital
queues one. Single scout, capital-only; the existing frontier-seek + scout-sweep
maneuvers (movement.rs) already drive dwarf_scout, so the AI stops diverting
combat units to scouting.
Tests: ai_builds_scout_when_buildable_and_none_owned +
ai_does_not_build_scout_without_its_tech; mc-ai 289/0 green. p3-22 → done.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>