feat(core/slice-1): TeleportAnimSequencer — define enums, record, event types

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/AcDream.Core/World/TeleportAnimSequencer.cs

@@ -0,0 +1,37 @@
+namespace AcDream.Core.World;
+
+// acclient.h:6871 — TeleportAnimState enum, verbatim order.
+public enum TeleportAnimState
+{
+    Off            = 0,
+    WorldFadeOut   = 1,
+    TunnelFadeIn   = 2,
+    Tunnel         = 3,
+    TunnelContinue = 4,
+    TunnelFadeOut  = 5,
+    WorldFadeIn    = 6,
+}
+
+/// <summary>Why the teleport was triggered — drives per-entry start state (spec §2.5).</summary>
+public enum TeleportEntryKind { Portal, Login, Death, Logout }
+
+/// <summary>
+/// Edge-triggered events the sequencer emits on the tick they first occur.
+/// Consumers drive audio / placement / LoginComplete from these; the sequencer
+/// has no dependency on any of those systems.
+/// </summary>
+public enum TeleportAnimEvent
+{
+    PlayEnterSound,    // Begin(): sound_ui_enter_portal
+    EnterTunnel,       // Off/WorldFade* -> Tunnel: world is now hidden
+    Place,             // Tunnel -> TunnelContinue: world loaded; place the player
+    PlayExitSound,     // TunnelFadeOut -> WorldFadeIn: sound_ui_exit_portal
+    FireLoginComplete, // WorldFadeIn -> Off: send GameAction 0xA1
+}
+
+/// <summary>Immutable per-frame snapshot from the sequencer.</summary>
+public readonly record struct TeleportAnimSnapshot(
+    TeleportAnimState State,
+    float FadeAlpha,       // 0 = clear world, 1 = full black
+    bool  ShowTunnel,      // true during TunnelFadeIn..TunnelFadeOut
+    bool  ShowPleaseWait); // true during TunnelContinue only