refactor: remove dead main_context field from Project Settings

The main_context field in Project Settings was stored but never used.
Nothing reads it to inject into AI context. System Prompt in AI Settings
already serves this purpose.

Removed:
- app_controller.py: ui_project_main_context state variable and all refs
- gui_2.py: Main Context File UI section from Projects panel
- project_manager.py: main_context from default_project()
- project.toml, manual_slop.toml, gencpp_manual_slop_template.toml: main_context entries

gencpp_manual_slop_template.toml

@@ -3,7 +3,6 @@
 [project]
 name = "gencpp"
 git_dir = ".git"
-main_context = "GenCpp: A C++ library for agenic code generation and analysis."
 word_wrap = true
 
 [paths]

manual_slop.toml

@@ -6,7 +6,6 @@ word_wrap = true
 summary_only = false
 auto_scroll_comms = true
 auto_scroll_tool_calls = true
-main_context = ""
 
 [output]
 output_dir = "./md_gen"

project.toml

@@ -1,8 +1,6 @@
 [project]
 name = "project"
 git_dir = ""
-system_prompt = ""
-main_context = ""
 execution_mode = "native"
 
 [output]

src/app_controller.py

@@ -254,7 +254,6 @@ class AppController:
   self.ui_files_base_dir: str = ""
   self.ui_shots_base_dir: str = ""
   self.ui_project_git_dir: str = ""
-  self.ui_project_main_context: str = ""
   self.ui_project_system_prompt: str = ""
   self.ui_project_execution_mode: str = "native"
   self.ui_gemini_cli_path: str = "gemini"
@@ -367,7 +366,6 @@ class AppController:
    'project_git_dir': 'ui_project_git_dir',
    'auto_add_history': 'ui_auto_add_history',
    'disc_new_name_input': 'ui_disc_new_name_input',
-   'project_main_context': 'ui_project_main_context',
    'gcli_path': 'ui_gemini_cli_path',
    'output_dir': 'ui_output_dir',
    'files_base_dir': 'ui_files_base_dir',
@@ -1186,7 +1184,6 @@ class AppController:
   proj_meta = self.project.get("project", {})
   self.ui_project_git_dir = proj_meta.get("git_dir", "")
   self.ui_project_conductor_dir = self.project.get('conductor', {}).get('dir', 'conductor')
-  self.ui_project_main_context = proj_meta.get("main_context", "")
   self.ui_project_system_prompt = proj_meta.get("system_prompt", "")
   self.ui_gemini_cli_path = self.project.get("gemini_cli", {}).get("binary_path", "gemini")
   self._update_gcli_adapter(self.ui_gemini_cli_path)
@@ -2381,7 +2378,6 @@ class AppController:
   proj_meta = self.project.get("project", {})
   self.ui_project_git_dir = proj_meta.get("git_dir", "")
   self.ui_project_system_prompt = proj_meta.get("system_prompt", "")
-  self.ui_project_main_context = proj_meta.get("main_context", "")
   self.ui_project_preset_name = proj_meta.get("active_preset")
   self.ui_gemini_cli_path = self.project.get("gemini_cli", {}).get("binary_path", "gemini")
   self.ui_auto_add_history = proj.get("discussion", {}).get("auto_add", False)
@@ -2812,7 +2808,6 @@ class AppController:
   self.ui_global_system_prompt = ''
   self.ui_base_system_prompt = ''
   self.ui_project_system_prompt = ''
-  self.ui_project_main_context = ''
   self.ui_active_persona = ''
   self.ui_active_tool_preset = None
   self.ui_active_bias_profile = None
@@ -2982,7 +2977,6 @@ class AppController:
   proj["project"]["git_dir"] = self.ui_project_git_dir
   proj.setdefault("conductor", {})["dir"] = self.ui_project_conductor_dir
   proj["project"]["system_prompt"] = self.ui_project_system_prompt
-  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"]["auto_scroll_comms"] = self.ui_auto_scroll_comms

src/gui_2.py

@@ -2083,15 +2083,6 @@ class App:
    r.destroy()
    if d: self.ui_project_git_dir = d
   imgui.separator()
-  imgui.text("Main Context File")
-  ch, self.ui_project_main_context = imgui.input_text("##main_ctx", self.ui_project_main_context)
-  imgui.same_line()
-  if imgui.button("Browse##ctx"):
-   r = hide_tk_root()
-   p = filedialog.askopenfilename(title="Select Main Context File")
-   r.destroy()
-   if p: self.ui_project_main_context = p
-  imgui.separator()
   imgui.text("Output Dir")
   ch, self.ui_output_dir = imgui.input_text("##out_dir", self.ui_output_dir)
   imgui.same_line()

src/project_manager.py

@@ -100,7 +100,7 @@ def default_project(name: str = "unnamed") -> dict[str, Any]:
  [C: tests/test_deepseek_infra.py:test_default_project_includes_reasoning_role, tests/test_discussion_takes.py:TestDiscussionTakes.setUp, tests/test_history_management.py:test_history_persistence_across_turns, tests/test_history_management.py:test_save_separation, tests/test_project_manager_modes.py:test_default_project_execution_mode, tests/test_project_manager_modes.py:test_load_save_execution_mode, tests/test_project_serialization.py:TestProjectSerialization.test_default_roles_include_context, tests/test_project_serialization.py:TestProjectSerialization.test_fileitem_roundtrip]
  """
  return {
-  "project":     {"name": name, "git_dir": "", "system_prompt": "", "main_context": "", "execution_mode": "native"},
+  "project":     {"name": name, "git_dir": "", "system_prompt": "", "execution_mode": "native"},
   "output":      {"output_dir": "./md_gen"},
   "files":       {"base_dir": ".", "paths": [], "tier_assignments": {}},
   "screenshots": {"base_dir": ".", "paths": []},