SIMD Refactor: Merge simd-dev into dev (#55)

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: aider (openrouter/anthropic/claude-sonnet-4) <aider@aider.chat>
Co-authored-by: Warp <agent@warp.dev>

lib/core/tvalue/tvalue.cs

@@ -0,0 +1,40 @@
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+namespace QuanTAlib;
+
+/// <summary>
+/// A lightweight struct representing a time-value pair.
+/// Pure data type: 16 bytes (long + double).
+/// </summary>
+[SkipLocalsInit]
+[StructLayout(LayoutKind.Auto)]
+public readonly record struct TValue(long Time, double Value)
+{
+    public DateTime AsDateTime => new(Time, DateTimeKind.Utc);
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public TValue(DateTime time, double value)
+        : this(time.Kind == DateTimeKind.Utc ? time.Ticks : time.ToUniversalTime().Ticks, value)
+    {
+    }
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static explicit operator double(TValue tv) => tv.Value;
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static implicit operator DateTime(TValue tv) => new(tv.Time, DateTimeKind.Utc);
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public override string ToString()
+    {
+        string valueStr = Value switch
+        {
+            double.PositiveInfinity => ((char)0x221E).ToString(),
+            double.NegativeInfinity => "-" + (char)0x221E,
+            _ when double.IsNaN(Value) => "NaN",
+            _ => Value.ToString("F2"),
+        };
+        return $"[{AsDateTime:yyyy-MM-dd HH:mm:ss}, {valueStr}]";
+    }
+}