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>

tests/AcDream.Core.Tests/Spells/RetailSpellFormulaTests.cs

@@ -0,0 +1,59 @@
+using AcDream.Core.Spells;
+
+namespace AcDream.Core.Tests.Spells;
+
+public sealed class RetailSpellFormulaTests
+{
+    [Theory]
+    [InlineData(1u, 1)]
+    [InlineData(6u, 6)]
+    [InlineData(0x6Eu, 6)]
+    [InlineData(0x70u, 7)]
+    [InlineData(0xC0u, 7)]
+    [InlineData(0xC1u, 8)]
+    [InlineData(7u, 0)]
+    public void RoughHeuristic_UsesFormulaPowerComponent(uint component, int expected)
+        => Assert.Equal(expected,
+            RetailSpellFormula.InqSpellLevelByRoughHeuristic([component]));
+
+    [Fact]
+    public void CustomizeForAccount_IsDeterministic_AndOnlyChangesTapers()
+    {
+        uint[] formula = [6u, 63u, 10u, 64u, 20u, 30u, 65u, 40u];
+
+        IReadOnlyList<uint> first = RetailSpellFormula.CustomizeForAccount(
+            formula, 3u, "testaccount");
+        IReadOnlyList<uint> second = RetailSpellFormula.CustomizeForAccount(
+            formula, 3u, "testaccount");
+
+        Assert.Equal(first, second);
+        Assert.Equal(formula[0], first[0]);
+        Assert.Equal(formula[1], first[1]);
+        Assert.Equal(formula[2], first[2]);
+        Assert.InRange(first[3], 63u, 74u);
+        Assert.Equal(formula[4], first[4]);
+        Assert.Equal(formula[5], first[5]);
+        Assert.InRange(first[6], 63u, 74u);
+        Assert.Equal(formula[7], first[7]);
+    }
+
+    [Theory]
+    [InlineData(1u, 1)]
+    [InlineData(2u, 2)]
+    [InlineData(3u, 3)]
+    [InlineData(0x6Eu, 3)]
+    [InlineData(0x70u, 4)]
+    [InlineData(0xC1u, 4)]
+    public void ScarabOnlyFormula_KeepsPowerAndAppendsRetailTaperCount(
+        uint powerComponent,
+        int expectedTapers)
+    {
+        IReadOnlyList<uint> result = RetailSpellFormula.InqScarabOnlyFormula(
+            [powerComponent, 63u, 10u, 64u]);
+
+        Assert.Equal(powerComponent, result[0]);
+        Assert.Equal(expectedTapers, result.Count(component => component == 0xBCu));
+        Assert.DoesNotContain(63u, result);
+        Assert.DoesNotContain(10u, result);
+    }
+}