feat(vfx): Phase E.3 particle system + hook wiring + registry

Full runtime particle pipeline consuming Phase E.1's animation hooks.
13 motion integrators, per-emitter particle pools with overwrite-oldest
eviction, colour / scale / alpha interpolation over life, and a
ParticleHookSink routing CreateParticle / DestroyParticle / StopParticle /
CreateBlockingParticle hooks from the animation-hook router.

Core layer:
- ParticleSystem: handle-based emitter pool, per-tick emission
  accumulator (retail Birthrate = time-between-spawns → our emit rate
  via 1/B), 13 integrators covering the full ParticleType enum:
  Still, LocalVelocity, GlobalVelocity, 7 Parabolic variants (all
  apply Gravity * dt to velocity), Swarm (orbital drift),
  Explode (outward from anchor), Implode (inward to anchor, dies at
  convergence).
- EmitterDescRegistry: id-keyed EmitterDesc cache with fallback-to-
  default for unknown ids. Replaces the dat-loaded path until
  Chorizite.DatReaderWriter exposes ParticleEmitterInfo (v2.1.7 does
  not; upgraded from 2.1.4 anyway for future types).
- ParticleHookSink: wires the full hook family:
  - CreateParticleHook → SpawnEmitterById at entity pose + hook offset
  - CreateBlockingParticleHook → marker only (blocking semantics live
    in the sequencer not here)
  - DestroyParticleHook → StopEmitter(handle, fadeOut=false)
  - StopParticleHook   → StopEmitter(handle, fadeOut=true)
  - (Default/CallPES deferred until PhysicsScript dat is loadable)

GameWindow integration:
- ParticleSystem created eagerly (no driver dep), sink registered with
  hook router, Tick advanced per OnRender frame after animation tick so
  hooks fired this frame get integrated.

Tests (11 new): spawn-handle, emit-over-time steady state, lifetime
death curve, LocalVelocity movement, Parabolic gravity arc, Explode
outward trajectory, StopEmitter instant kill vs fadeOut, MaxParticles
cap enforcement, registry default fallback, registry custom
registration.

Upgraded Chorizite.DatReaderWriter 2.1.4 → 2.1.7 across Core + Cli.

Build green, 508 tests pass (up from 497).

Ref: r04 §2 (CParticleManager), §3 (13 integrators), §6 (PhysicsScript).
Renderer (instanced billboarded quads in translucent pass) ships next
commit; this one covers the data / logic / wiring layer in full.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/AcDream.Core/AcDream.Core.csproj

@@ -8,7 +8,7 @@
   </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="BCnEncoder.Net" Version="2.2.1" />
-    <PackageReference Include="Chorizite.DatReaderWriter" Version="2.1.4" />
+    <PackageReference Include="Chorizite.DatReaderWriter" Version="2.1.7" />
     <PackageReference Include="Serilog" Version="4.0.2" />
   </ItemGroup>
   <ItemGroup>