Restructure solution layout by module

src/Signals/StellaOps.Signals/Parsing/ICallgraphParser.cs

@@ -0,0 +1,21 @@
+using System.IO;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace StellaOps.Signals.Parsing;
+
+/// <summary>
+/// Parses raw callgraph artifacts into normalized structures.
+/// </summary>
+public interface ICallgraphParser
+{
+    /// <summary>
+    /// Language identifier handled by the parser (e.g., java, nodejs).
+    /// </summary>
+    string Language { get; }
+
+    /// <summary>
+    /// Parses the supplied artifact stream.
+    /// </summary>
+    Task<CallgraphParseResult> ParseAsync(Stream artifactStream, CancellationToken cancellationToken);
+}