feat(gui): Remove ui_summary_only global toggle

The ui_summary_only global aggregation toggle was redundant with per-file flags
(auto_aggregate, force_full). Removed:
- Checkbox from Projects panel (gui_2.py)
- State variable and project load/save (app_controller.py)

Per-file flags remain the intended mechanism for controlling aggregation.

Tests added to verify removal and per-file flag functionality.

config.toml

@@ -10,14 +10,9 @@ system_prompt = "Overridden Prompt"
 
 [projects]
 paths = [
-    "C:/projects/gencpp/gencpp_sloppy.toml",
-    "C:\\projects\\manual_slop\\tests\\artifacts\\temp_livecontextsim.toml",
-    "C:\\projects\\manual_slop\\tests\\artifacts\\temp_liveaisettingssim.toml",
-    "C:\\projects\\manual_slop\\tests\\artifacts\\temp_livetoolssim.toml",
-    "C:\\projects\\manual_slop\\tests\\artifacts\\temp_liveexecutionsim.toml",
-    "C:\\projects\\manual_slop\\tests\\artifacts\\temp_project.toml",
+    "C:/projects/gencpp/.ai/gencpp_sloppy.toml",
 ]
-active = "C:/projects/gencpp/gencpp_sloppy.toml"
+active = "C:/projects/gencpp/.ai/gencpp_sloppy.toml"
 
 [gui]
 separate_message_panel = false
@@ -34,9 +29,9 @@ separate_tier4 = false
 separate_external_tools = false
 
 [gui.show_windows]
-"Context Hub" = true
-"Files & Media" = true
-"AI Settings" = true
+"Context Hub" = false
+"Files & Media" = false
+"AI Settings" = false
 "MMA Dashboard" = false
 "Task DAG" = true
 "Usage Analytics" = true
@@ -53,12 +48,12 @@ separate_external_tools = false
 Message = false
 Response = false
 "Tool Calls" = false
-Theme = true
+Theme = false
 "Log Management" = false
 Diagnostics = false
 "External Tools" = false
 "Shader Editor" = false
-"Session Hub" = false
+"Session Hub" = true
 
 [theme]
 palette = "Nord Dark"