Slice Combat Depth (MC-2): enemy-variety server spine — Spitter, Swarmer, 4-type mix (DR-041)

Adds the server-authoritative mechanics for three new enemy archetypes on top of
the Grunt/Charger base, plus the weighted wave-composition that introduces them:

- Spitter: a ranged Husk variant (SpitterState) that holds a preferred range-band
  (advance/retreat/hold via EnemyAIMath.BandVelocity) and fires a telegraphed,
  dodgeable EnemyProjectile. New server EnemyProjectileMoveSystem (integrate +
  store LastStep) + EnemyProjectileDamageSystem (region-filtered swept hit-test
  rebuilt from LastStep — DR-018 anti-tunnelling; players use HitRadius, structures
  a const radius; at-most-once destroy). Concurrent-spit soft cap, soft-fail retry.
- Swarmer: marker tag + deterministic cluster spawn (1 slot = 1 pack;
  EnemyAIMath.ClusterOffset), MaxAlive counts ENTITIES so a pack defers if it
  won't fit.
- 4-type weighted mix: MixBands -> ZoneEnemyMath.WaveSlots/KindForSlot/
  PackSizeForSlot drives both the expedition director and (fork-4a) the base siege,
  with a mandatory MaxAlive cap. Legacy WaveSize/IsChargerSlot kept + parity-tested.
- Discriminator stays component-presence (no enum in Bursted systems): query-
  partition guards keep each enemy moved by exactly one EnemyAISystem pass
  (sole-Position-writer). EnemyTelegraph.IsCharger -> Kind byte for the client cue.

New authoring (Spitter/Swarmer/EnemyProjectile) + expanded director authorings with
tunable mix/cluster defaults. 13 new EditMode tests (mix composition + legacy parity,
band/cluster math, projectile move + cross-region + swept anti-tunnelling regressions);
full suite green before commit.

Dormant until the prefab/subscene wiring lands (next): the new systems guard on
TryGetSingleton/RequireForUpdate, so with no prefabs wired the new types stay inert.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Assets/_Project/Scripts/Simulation/Combat/SpitterComponents.cs

@@ -0,0 +1,45 @@
+using Unity.Entities;
+
+namespace ProjectM.Simulation
+{
+    /// <summary>
+    /// MC-2 — server-only Spitter "reposition" brain state. Component PRESENCE is the Spitter discriminator (no
+    /// enum / brain byte — honours the Burst cross-assembly-enum rule; EnemyAISystem is Bursted): a Husk variant
+    /// baked with SpitterState is driven by the ranged range-band branch, mutually exclusive with the Charger
+    /// branch (the AI partitions Spitter = .WithAll&lt;EnemyTag,SpitterState&gt;().WithNone&lt;LungeState&gt;() so no
+    /// enemy is ever double-moved). The Spitter holds a PREFERRED RANGE band from its target — retreating if too
+    /// close, advancing if too far — and fires a TELEGRAPHED, dodgeable projectile on its OWN fire gate. If
+    /// cornered (no retreat room) within CorneredRange it falls back to the Grunt seek+strike. NOT a [GhostField]
+    /// (only server systems read it). All ticks via TickUtil.NonZero; compared with NetworkTick only.
+    /// </summary>
+    public struct SpitterState : IComponentData
+    {
+        /// <summary>Band centre: the distance the Spitter tries to hold from its target (world units).</summary>
+        public float PreferredRange;
+
+        /// <summary>Half-width dead-zone around PreferredRange; inside [pref-tol, pref+tol] the Spitter holds.</summary>
+        public float RangeTolerance;
+
+        /// <summary>Muzzle speed baked onto the spit projectile (world units/second).</summary>
+        public float ProjectileSpeed;
+
+        /// <summary>If the target closes within this distance AND the Spitter can't retreat, it melee-falls-back.</summary>
+        public float CorneredRange;
+
+        /// <summary>Telegraph wind-up lead in ticks before the spit fires (the dodge window). Baked (v1 not
+        /// live-tunable); keep >= ~24 (> interp delay) so a player reacting to the aim-line can clear the shot.</summary>
+        public int WindupTicks;
+
+        /// <summary>Server-only fire gate: raw tick of the earliest tick it may spit again (NonZero; 0 = ready). Its
+        /// OWN gate, never EnemyAttackCooldown. Compared via NetworkTick.IsNewerThan.</summary>
+        public uint NextShotTick;
+    }
+
+    /// <summary>
+    /// MC-2 — pure marker for a Swarmer "surround" enemy: mechanically a Grunt (NO AI branch — it falls through the
+    /// Grunt seek+strike pass) with swarm-tuned baked EnemyStats (fast, low-HP, fast frequent low-chip bites). The
+    /// tag drives only (a) the director's CLUSTER spawn (PackSize swarmers in one tick) and (b) a client tint. Keeps
+    /// EnemyTag + RegionTag like every Husk, so readability / health-bars / damage / region-AI all work unchanged.
+    /// </summary>
+    public struct SwarmerTag : IComponentData { }
+}