Add a working NPC AI engine (brains, orders, combat styles, aranha species)

[cybervand]

(note: I'm going to be real with you lads. This PR was almost entirely
done by Fable 5 for the creation of the engine and GPT 5.6 Sol using Ghidra
for the reverse engineering. There was alot of input and testing done by me.
It works but there is still alot of work for ai to be done. what helped tremendously,
was building my own tools for the help of the reverse engineering. that will come shortly.)

Replaces the AIEngine stub with a complete server-side NPC brain system,
developed and play-tested against live gameplay on the Firefall client:

• Brains: one BrainState per living NPC, 4 Hz think, target selection with
  memory, leash and return-home, per-entity passive override
• Orders API: AttackEntity / DefendPoint / MoveTo / FollowEntity records as
  the seam between content (encounters, missions) and brains
• Behavior profiles derived from SDB data only (no per-monster config):
  speeds and faction from the monster row, movement class from the rig name
  (ground / flying / stationary / climber), combat style from real weapon
  ranges (melee / ranged / sniper / artillery hold distances)
• Combat: ballistic aim solutions from ammunition gravity and speed (low
  arc, high arc for artillery and blocked muzzles, 45-degree maximum-reach,
  hold-fire when the target is above ballistic reach), muzzle-blocked
  probing, cliff/verticality handling, visible NPC projectiles via
  AbilityProjectileFired
• Creature separation: body-width discs prevent packs from stacking into
  one point
• Species layer: partial-class files per species; AIEngine.Aranha.cs ships
  first with hull climbing and latching, per-NPC perch points, pounce leaps
  at players, random leaps onto thumper hulls, and pack-hunting roles
  (direct attackers, circling flankers, leapers, per-NPC gait)

The thumper encounter gets its defense gameplay on top of the AI
(second commit):

• Escalating attack waves while the thumper drills, spawned on a
  terrain-snapped ring: workers first, a sieger from wave 2, a spitting
  thresher from wave 4. Half of each wave is ordered onto the thumper via
  the Orders API; the other half runs default AI and hunts players.
• Thumper health: attackers reduce its integrity; at zero the thumper is
  destroyed and the encounter fails.
• On both endings - the thumper is destroyed, or it completes and leaves -
  all wave-spawned enemies are removed with it.
• Hive sites (HiveIndex + "hive add | list | clear" admin command):
  authored underground-population zones, persisted as JSON per zone.
  Thumping inside a hive wakes a dense, fast eruption instead of the
  default trickle - wave interval, size, and alive cap all scale with
  distance to the hive center.

Also fixes a crash found while testing this PR with LoadMapsCollision
enabled (third commit): SegmentRayCast read a body handle from a static
collidable when a projectile hit zone terrain, which stops the process
with a Bepu assertion.

New admin commands:

• hive add [radius] [burst] - plants a hive site at your position
  (defaults: radius 120 m, burst 50). Thumping inside the zone will result
  with the death of the thumper, its a dense wave, thumping near the edges
  will have a falloff.
• hive list - lists the hive sites of the zone with distance to you
• hive clear - removes all hive sites of the zone
• npcfx show | muzzle <fraction> | hardpoint <id> | offset <x> <y> <z> -
  live-tunes the NPC projectile FX anchoring (muzzle height on the rig
  capsule, client hardpoint, visual offset)
• npcfx aimpoint - firing-range debug mode: armed NPCs stand and fire at
  a fixed point instead of hunting players. (this is used for finetuning,
  the ai in the engine has a firing offset of 0,0,0 which will result in
  some of them unable to shoot)
• pacify <on|off> [all] - toggles NPC aggression for the admin target or
  for every live NPC. Useful for finetuning attacks

Supporting additions:

• PhysicsEngine.GetGroundHeight: static-geometry ground probe with an
  optional walkable kinematic body (lets climbers walk on thumper hulls)
• MovementRelay.BroadcastCharacterPose: extracted from CharacterMovementInput
  and reused for server-moved NPCs (also keeps NPC physics bodies in sync)
• ThumperEntity: CurrentHealth / Damage / IsAttackable / IsDestroyed
• CharacterEntity.GetNpcMuzzleHeight: muzzle height from the scaled rig capsule

Not in this PR, coming as follow-ups: mesh-accurate NPC hitboxes built
from bMesh render geometry (we have this working; it needs a careful merge
with the new pose-shape hit system from the weapon-sim update), and the
species roster work for the remaining aranha variants.

All comments follow ASD-STE100 (Simplified Technical English).

Co-Authored-By: Claude Fable 5 noreply@anthropic.com

🤖 Generated with Claude Code

[cybervand]

Here is the hive system and the AI waves from this PR running live (2 min, unlisted):

https://youtu.be/JMySznVJ64U

A hive site is planted with the admin command, then a thumper wakes it. The waves spawn, half attack the thumper, the rest hunt the player - climbing, leaping, and pack behavior all visible.