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.

src/app_controller.py

@@ -230,7 +230,6 @@ class AppController:
   self.ui_project_system_prompt: str = ""
   self.ui_gemini_cli_path: str = "gemini"
   self.ui_word_wrap: bool = True
-  self.ui_summary_only: bool = False
   self.ui_auto_add_history: bool = False
   self.ui_active_tool_preset: str | None = None
   self.ui_global_system_prompt: str = ""
@@ -912,7 +911,6 @@ class AppController:
   self.ui_gemini_cli_path = self.project.get("gemini_cli", {}).get("binary_path", "gemini")
   self._update_gcli_adapter(self.ui_gemini_cli_path)
   self.ui_word_wrap = proj_meta.get("word_wrap", True)
-  self.ui_summary_only = proj_meta.get("summary_only", False)
   self.ui_auto_add_history = disc_sec.get("auto_add", False)
   self.ui_global_system_prompt = self.config.get("ai", {}).get("system_prompt", "")
   
@@ -2006,7 +2004,6 @@ class AppController:
   self.ui_auto_scroll_comms = proj.get("project", {}).get("auto_scroll_comms", True)
   self.ui_auto_scroll_tool_calls = proj.get("project", {}).get("auto_scroll_tool_calls", True)
   self.ui_word_wrap = proj.get("project", {}).get("word_wrap", True)
-  self.ui_summary_only = proj.get("project", {}).get("summary_only", False)
   agent_tools_cfg = proj.get("agent", {}).get("tools", {})
   self.ui_agent_tools = {t: agent_tools_cfg.get(t, True) for t in models.AGENT_TOOL_NAMES}
   # MMA Tracks
@@ -2458,7 +2455,6 @@ class AppController:
   proj["project"]["main_context"] = self.ui_project_main_context
   proj["project"]["active_preset"] = self.ui_project_preset_name
   proj["project"]["word_wrap"] = self.ui_word_wrap
-  proj["project"]["summary_only"] = self.ui_summary_only
   proj["project"]["auto_scroll_comms"] = self.ui_auto_scroll_comms
   proj["project"]["auto_scroll_tool_calls"] = self.ui_auto_scroll_tool_calls
   proj.setdefault("gemini_cli", {})["binary_path"] = self.ui_gemini_cli_path