Add live debugger frontend and mutex stall recovery (#383)

src/SharpEmu.Debugger/Protocol/IDebugProtocol.cs

@@ -0,0 +1,33 @@
+// Copyright (C) 2026 SharpEmu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+namespace SharpEmu.Debugger.Protocol;
+
+/// <summary>
+/// Frames debugger traffic on a connection. A protocol turns bytes into
+/// <see cref="DebugRequest"/> objects and serialises <see cref="DebugResponse"/>
+/// replies plus asynchronous events (stops, resumes, termination) back to the
+/// client. Swapping the implementation (line-delimited JSON today, a GDB remote
+/// serial stub later) leaves the session and server untouched.
+/// </summary>
+public interface IDebugProtocol
+{
+    /// <summary>A short protocol name reported in the handshake.</summary>
+    string Name { get; }
+
+    /// <summary>
+    /// Reads the next request, or null at end of stream. Parse failures are
+    /// surfaced as a request with a reserved error command rather than throwing.
+    /// </summary>
+    Task<DebugRequest?> ReadRequestAsync(TextReader reader, CancellationToken cancellationToken);
+
+    /// <summary>Writes a reply to a request.</summary>
+    Task WriteResponseAsync(TextWriter writer, DebugResponse response, CancellationToken cancellationToken);
+
+    /// <summary>Writes an unsolicited event (for example a stop notification).</summary>
+    Task WriteEventAsync(
+        TextWriter writer,
+        string eventName,
+        IReadOnlyDictionary<string, object?> data,
+        CancellationToken cancellationToken);
+}