feat(context): Implement view mode UI in context composition panel

tests/test_context_composition_phase4.py

@@ -0,0 +1,35 @@
+import pytest
+from src.gui_2 import App
+from src.models import FileItem
+
+def test_view_mode_initialization():
+    app = App()
+    # Mock imgui
+    from imgui_bundle import imgui
+    
+    app.context_files = [
+        FileItem(path="test1.py"),
+        FileItem(path="test2.py", view_mode="full")
+    ]
+    
+    # We test the model defaults and the rendering assignment logic indirectly.
+    assert app.context_files[0].view_mode == "full" # Default from FileItem Model
+    assert app.context_files[1].view_mode == "full"
+
+def test_batch_view_mode_change():
+    app = App()
+    
+    f1 = FileItem(path="test1.py", view_mode="full")
+    f2 = FileItem(path="test2.py", view_mode="full")
+    
+    app.context_files = [f1, f2]
+    app.ui_selected_context_files = {"test1.py"}
+    
+    # Simulate clicking "Skeleton" batch button
+    for f in app.context_files:
+        f_path = f.path if hasattr(f, "path") else str(f)
+        if f_path in app.ui_selected_context_files:
+            f.view_mode = "skeleton"
+            
+    assert f1.view_mode == "skeleton"
+    assert f2.view_mode == "full" # not selected