fix: Prevent infinite compilation loop in Unity 6 when using wait_for_ready (#559)

* fix: Prevent infinite compilation loop in Unity 6 when using wait_for_ready

Skip WaitForUnityReadyAsync when compileRequested is true. The
EditorApplication.update polling doesn't survive domain reloads
properly in Unity 6, causing infinite compilation loops.

When compilation is requested, return immediately and let the
client poll editor_state resource instead.

Fixes #557

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* fix: Use actuallyWaited for hint message consistency

Address code review feedback: when compile was requested and we skip
WaitForUnityReadyAsync, the hint should correctly indicate that the
client needs to poll editor_state, not claim the editor is ready.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* refactor: Gate Unity 6 fix with version check and rename variable

Address code review feedback:
- Use UNITY_6000_0_OR_NEWER preprocessor directive to only apply the
  compilation wait bypass on Unity 6+, preserving original behavior
  for earlier versions
- Rename actuallyWaited to shouldWaitForReady for clarity, as it
  represents the decision to wait rather than a post-hoc result

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

MCPForUnity/Editor/Tools/RefreshUnity.cs

@@ -90,7 +90,17 @@ namespace MCPForUnity.Editor.Tools
                 return new ErrorResponse($"refresh_failed: {ex.Message}");
             }
 
-            if (waitForReady)
+            // Unity 6+ fix: Skip wait_for_ready when compile was requested.
+            // The EditorApplication.update polling in WaitForUnityReadyAsync doesn't survive
+            // domain reloads properly in Unity 6+, causing infinite compilation loops.
+            // When compilation is requested, return immediately and let client poll editor_state.
+            // Earlier Unity versions retain the original behavior.
+#if UNITY_6000_0_OR_NEWER
+            bool shouldWaitForReady = waitForReady && !compileRequested;
+#else
+            bool shouldWaitForReady = waitForReady;
+#endif
+            if (shouldWaitForReady)
             {
                 try
                 {
@@ -122,7 +132,7 @@ namespace MCPForUnity.Editor.Tools
                 refresh_triggered = refreshTriggered,
                 compile_requested = compileRequested,
                 resulting_state = resultingState,
-                hint = waitForReady
+                hint = shouldWaitForReady
                     ? "Unity refresh completed; editor should be ready."
                     : "If Unity enters compilation/domain reload, poll editor_state until ready_for_tools is true."
             });