Delete HardpointTransforms; mount direction and arc become sim data

Entity.HardpointTransforms was written only by Unity (EntityInstance.cs),
so the simulation's notion of where a gun points was a readback from a
renderer that never runs headless -- Combat.cs threw KeyNotFoundException
on the first combat tick outside Unity. Deletes the field, its writer, and
the readback branch in Behavior.Direction, leaving the item-rotation path
(the same convention reaction thrusters use, R6) as the only source of
mount direction.

Adds FireControl (ServerShared), a static class owning whether a weapon
bears on a point: MountDirection (planar, from ItemRotation), ArcFor (the
per-hardpoint HardpointData.FiringArc override, falling back to the new
GameplaySettings.FiringArc default of 120), and InArc (the planar dot-cone
test, R7 -- target height never enters it, and an arc of 360+ passes
unconditionally so a turret hardpoint needs no new type, just a number).
Combat.cs and TurretController.cs now gate AI fire through InArc instead
of the old hardcoded 0.99 dot-product test against a live Unity transform.
Settings.cs drops AgentFiringMinDot, which was declared and read by
nothing.

docs/fire-control-cut.md, Cut 1.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Assets/Scripts/ServerShared/ItemData.cs

@@ -543,6 +543,9 @@ public class HardpointData
     [Inspectable, JsonProperty("transform"), Key(3)] public string Transform;
     [Inspectable, JsonProperty("rotation"), Key(4)] public ItemRotation Rotation;
     [Inspectable, JsonProperty("armor"), Key(5)] public float Armor;
+    // Full arc width in degrees a weapon on this hardpoint may bear across; 0 means "use
+    // GameplaySettings.FiringArc" (docs/fire-control-cut.md R6). Turrets author 360 (Q1).
+    [Inspectable, JsonProperty("firingArc"), Key(6)] public float FiringArc;
 
     public override string ToString()
     {