Build 36b76cc

sentry: per-bot approach diversity, coordinated push, true flanking

3 features for more human-like sentry engagement:

- Per-bot lateral offset (100-250u): even-index bots go right, odd go
  left. Uses flank axis when available, vertical approach spread otherwise.
  No two bots cluster at the identical approach point.

- Coordinated push via teammate sensing: first bot to arrive at safety
  distance (>600u from sentry) counts other bots already committed to
  SCHED_ATTACK_SENTRY_GUN. If a teammate is already on the sentry, this
  bot waits (stopMoving, 8s timeout) until the other bot arrives in
  position. When two+ bots are ready, both release simultaneously with
  a "Go go go!" voice command.

- True flanking via sentry-facing-perpendicular waypoint search: the
  sentry's current targeting enemy (getSentryEnemy) determines its facing
  direction. Waypoints with high perpendicular offset (>200u) from this
  axis and within 300-1500u of sentry are scored by (perpDist - 0.2*dist).
  Spy requires hidden flank (visibility table); soldier/demo/scout can
  flank openly. Flank is suppressed if corner-peek is available (shorter,
  also hidden).