feat: port retail magic lifecycle and retained spell UI

Complete the retail cast-intent, target, component, enchantment, and busy-state paths; mount the DAT-authored spell bar, spellbook, component book, effects panels, and shared panel lifecycle; and add scoped input plus conformance coverage.

Co-Authored-By: Codex <noreply@openai.com>

src/AcDream.Core/Spells/EnchantmentRegistryProjection.cs

@@ -0,0 +1,67 @@
+using System;
+using System.Collections.Generic;
+
+namespace AcDream.Core.Spells;
+
+/// <summary>
+/// Pure port of retail's ordinary in-effect registry projection:
+/// <c>CEnchantmentRegistry::GetEnchantmentsInEffect @ 0x00594540</c>,
+/// <c>GetEnchantmentsInEffectFromList @ 0x00594430</c>,
+/// <c>Duel @ 0x005942B0</c>, and <c>Enchantment::Duel @ 0x005CACE0</c>.
+/// </summary>
+public static class EnchantmentRegistryProjection
+{
+    /// <summary>
+    /// Merges multiplicative then additive records and retains one winner per
+    /// spell category. Higher power wins; equal power is replaced only by a
+    /// later start time. Vitae and cooldown registries do not participate.
+    /// </summary>
+    public static IReadOnlyList<ActiveEnchantmentRecord> GetEnchantmentsInEffect(
+        IEnumerable<ActiveEnchantmentRecord> enchantments)
+    {
+        ArgumentNullException.ThrowIfNull(enchantments);
+        ActiveEnchantmentRecord[] source = enchantments as ActiveEnchantmentRecord[]
+            ?? [.. enchantments];
+        var result = new List<ActiveEnchantmentRecord>();
+        DuelList(source, bucket: 1u, result);
+        DuelList(source, bucket: 2u, result);
+        return result;
+    }
+
+    private static void DuelList(
+        IReadOnlyList<ActiveEnchantmentRecord> source,
+        uint bucket,
+        List<ActiveEnchantmentRecord> result)
+    {
+        for (int sourceIndex = 0; sourceIndex < source.Count; sourceIndex++)
+        {
+            ActiveEnchantmentRecord candidate = source[sourceIndex];
+            if (candidate.Bucket != bucket) continue;
+
+            int incumbentIndex = result.FindIndex(existing =>
+                existing.SpellCategory == candidate.SpellCategory);
+            if (incumbentIndex >= 0)
+            {
+                ActiveEnchantmentRecord incumbent = result[incumbentIndex];
+                if (!CandidateWins(incumbent, candidate))
+                    continue;
+                // Retail removes the losing node, then appends the winner.
+                result.RemoveAt(incumbentIndex);
+            }
+            result.Add(candidate);
+        }
+    }
+
+    private static bool CandidateWins(
+        ActiveEnchantmentRecord incumbent,
+        ActiveEnchantmentRecord candidate)
+    {
+        // Retail Enchantment::_power_level is signed int even though the wire
+        // field is read as four raw bytes.
+        int incumbentPower = unchecked((int)incumbent.PowerLevel);
+        int candidatePower = unchecked((int)candidate.PowerLevel);
+        return candidatePower > incumbentPower
+            || (candidatePower == incumbentPower
+                && candidate.StartTime > incumbent.StartTime);
+    }
+}