Initial import of the CBDDC codebase with docs and tests. Add a .NET-focused gitignore to keep generated artifacts out of source control.

tests/ZB.MOM.WW.CBDDC.Core.Tests/PerformanceRegressionTests.cs

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+using System.Diagnostics;
+using System.Text.Json;
+using ZB.MOM.WW.CBDDC.Core.Sync;
+
+namespace ZB.MOM.WW.CBDDC.Core.Tests;
+
+public class PerformanceRegressionTests
+{
+    private readonly RecursiveNodeMergeConflictResolver _resolver;
+    private readonly Dictionary<string, int> _limits;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="PerformanceRegressionTests"/> class.
+    /// </summary>
+    public PerformanceRegressionTests()
+    {
+        _resolver = new RecursiveNodeMergeConflictResolver();
+
+        // Load limits
+        var json = File.ReadAllText("benchmark_limits.json");
+        _limits = JsonSerializer.Deserialize<Dictionary<string, int>>(json) ?? new Dictionary<string, int>();
+    }
+
+    private Document CreateDoc(string key, object data, HlcTimestamp ts)
+    {
+        var json = JsonSerializer.Serialize(data);
+        var element = JsonDocument.Parse(json).RootElement;
+        return new Document("test", key, element, ts, false);
+    }
+
+    private OplogEntry CreateOp(string key, object data, HlcTimestamp ts)
+    {
+        var json = JsonSerializer.Serialize(data);
+        var element = JsonDocument.Parse(json).RootElement;
+        return new OplogEntry("test", key, OperationType.Put, element, ts, string.Empty);
+    }
+
+    /// <summary>
+    /// Verifies simple recursive merge operations stay within configured performance limits.
+    /// </summary>
+    [Fact]
+    public void RecursiveMerge_Simple_ShouldBeWithinLimits()
+    {
+        int iterations = 10000;
+        string limitKey = "RecursiveMerge_Simple_10k_Ops_MaxMs";
+
+        var ts1 = new HlcTimestamp(100, 0, "n1");
+        var ts2 = new HlcTimestamp(200, 0, "n2");
+        var doc = CreateDoc("k1", new { name = "Alice", age = 30 }, ts1);
+        var op = CreateOp("k1", new { name = "Bob", age = 31 }, ts2);
+
+        // Warmup
+        for (int i = 0; i < 100; i++) _resolver.Resolve(doc, op);
+
+        // Run
+        var sw = Stopwatch.StartNew();
+        for (int i = 0; i < iterations; i++)
+        {
+            _resolver.Resolve(doc, op);
+        }
+        sw.Stop();
+
+        long elapsed = sw.ElapsedMilliseconds;
+        Console.WriteLine($"Executed {iterations} merges in {elapsed}ms");
+
+        if (_limits.TryGetValue(limitKey, out int maxMs))
+        {
+            elapsed.ShouldBeLessThan(maxMs, $"Performance regression! Expected < {maxMs}ms but took {elapsed}ms");
+        }
+        else
+        {
+            Console.WriteLine($"Warning: No limit found for key '{limitKey}'");
+        }
+    }
+
+    /// <summary>
+    /// Verifies deep array recursive merge operations stay within configured performance limits.
+    /// </summary>
+    [Fact]
+    public void RecursiveMerge_DeepArray_ShouldBeWithinLimits()
+    {
+        int iterations = 1000; // Lower iterations for heavier op
+        string limitKey = "RecursiveMerge_Array_1k_Ops_MaxMs";
+
+        var ts1 = new HlcTimestamp(100, 0, "n1");
+        var ts2 = new HlcTimestamp(200, 0, "n2");
+
+        var items = new List<object>();
+        for (int i = 0; i < 100; i++) items.Add(new { id = i.ToString(), val = i });
+
+        var doc = CreateDoc("k1", new { items = items }, ts1);
+        var op = CreateDoc("k1", new { items = items }, ts2).ToOplogEntry(OperationType.Put); // Same content to force id check traversal
+
+        // Warmup
+        _resolver.Resolve(doc, op);
+
+        // Run
+        var sw = Stopwatch.StartNew();
+        for (int i = 0; i < iterations; i++)
+        {
+            _resolver.Resolve(doc, op);
+        }
+        sw.Stop();
+
+        long elapsed = sw.ElapsedMilliseconds;
+        Console.WriteLine($"Executed {iterations} array merges in {elapsed}ms");
+
+        if (_limits.TryGetValue(limitKey, out int maxMs))
+        {
+            elapsed.ShouldBeLessThan(maxMs, $"Performance regression! Expected < {maxMs}ms but took {elapsed}ms");
+        }
+    }
+}
+
+public static class DocExt
+{
+    /// <summary>
+    /// Creates an operation log entry from a document instance.
+    /// </summary>
+    /// <param name="d">The source document.</param>
+    /// <param name="t">The operation type to apply to the created entry.</param>
+    /// <returns>A new operation log entry.</returns>
+    public static OplogEntry ToOplogEntry(this Document d, OperationType t)
+    {
+        return new OplogEntry(d.Collection, d.Key, t, d.Content, d.UpdatedAt, string.Empty);
+    }
+}