feat(gui): Implement Context Composition panel (Phase 3)

- Replaced placeholder with actual _render_context_composition_panel
- Shows current files with Auto-Aggregate and Force Full flags
- Shows current screenshots
- Preset dropdown to load existing presets
- Save as Preset / Delete Preset buttons
- Uses existing save_context_preset/load_context_preset methods

src/gui_2.py

@@ -728,7 +728,7 @@ class App:
        self._render_discussion_tab()
        imgui.end_tab_item()
       if imgui.begin_tab_item("Context Composition")[0]:
-       self._render_context_composition_placeholder()
+       self._render_context_composition_panel()
        imgui.end_tab_item()
       if imgui.begin_tab_item("Snapshot")[0]:
        self._render_snapshot_tab()
@@ -2085,10 +2085,57 @@ class App:
   else:
    imgui.text_disabled("Message & Response panels are detached.")
 
- def _render_context_composition_placeholder(self) -> None:
+ def _render_context_composition_panel(self) -> None:
   imgui.text("Context Composition")
   imgui.separator()
-  imgui.text_colored(C_LBL, "Coming in Phase 3...")
+  if imgui.begin_table("ctx_comp_table", 2, imgui.TableFlags_.resizable | imgui.TableFlags_.borders):
+   imgui.table_setup_column("File", imgui.TableColumnFlags_.width_stretch)
+   imgui.table_setup_column("Flags", imgui.TableColumnFlags_.width_fixed, 120)
+   imgui.table_headers_row()
+   for i, f_item in enumerate(self.files):
+    imgui.table_next_row()
+    imgui.table_set_column_index(0)
+    imgui.text(f_item.path if hasattr(f_item, "path") else str(f_item))
+    imgui.table_set_column_index(1)
+    if hasattr(f_item, "auto_aggregate"):
+     changed_agg, f_item.auto_aggregate = imgui.checkbox(f"Agg##cc{i}", f_item.auto_aggregate)
+     imgui.same_line()
+     changed_full, f_item.force_full = imgui.checkbox(f"Full##cc{i}", f_item.force_full)
+   imgui.end_table()
+  imgui.separator()
+  imgui.text("Screenshots")
+  for i, s in enumerate(self.screenshots):
+   imgui.text(s)
+  imgui.separator()
+  imgui.text("Presets")
+  presets = self.controller.project.get('context_presets', {})
+  preset_names = [""] + sorted(presets.keys())
+  active = getattr(self, "ui_active_context_preset", "")
+  if active not in preset_names:
+   active = ""
+  try:
+   idx = preset_names.index(active)
+  except ValueError:
+   idx = 0
+  ch, new_idx = imgui.combo("##ctx_preset", idx, preset_names)
+  if ch:
+   self.ui_active_context_preset = preset_names[new_idx]
+   if preset_names[new_idx]:
+    self.load_context_preset(preset_names[new_idx])
+  imgui.same_line()
+  changed, new_name = imgui.input_text("##new_preset", getattr(self, "ui_new_context_preset_name", ""))
+  if changed:
+   self.ui_new_context_preset_name = new_name
+  imgui.same_line()
+  if imgui.button("Save##ctx"):
+   if getattr(self, "ui_new_context_preset_name", "").strip():
+    self.save_context_preset(self.ui_new_context_preset_name.strip())
+    self.ui_new_context_preset_name = ""
+  imgui.same_line()
+  if imgui.button("Delete##ctx"):
+   if getattr(self, "ui_active_context_preset", ""):
+    self.delete_context_preset(self.ui_active_context_preset)
+    self.ui_active_context_preset = ""
 
  def _render_snapshot_tab(self) -> None:
   if imgui.begin_tab_bar("snapshot_tabs"):

tests/test_context_composition_panel.py

@@ -0,0 +1,42 @@
+import pytest
+import inspect
+
+
+def test_context_composition_panel_replaces_placeholder():
+    import src.gui_2 as gui_2
+
+    source = inspect.getsource(gui_2.App._gui_func)
+    assert "_render_context_composition_placeholder" not in source, (
+        "Placeholder should be replaced"
+    )
+    assert "_render_context_composition_panel" in source, (
+        "Should have _render_context_composition_panel"
+    )
+
+
+def test_context_composition_has_save_load_buttons():
+    import src.gui_2 as gui_2
+
+    source = inspect.getsource(gui_2.App._render_context_composition_panel)
+    assert "Save as Preset" in source or "save" in source.lower(), (
+        "Should have Save functionality"
+    )
+    assert "Load Preset" in source or "load" in source.lower(), (
+        "Should have Load functionality"
+    )
+
+
+def test_context_composition_shows_files():
+    import src.gui_2 as gui_2
+
+    source = inspect.getsource(gui_2.App._render_context_composition_panel)
+    assert "files" in source.lower() or "Files" in source, "Should show files"
+
+
+def test_context_composition_has_preset_list():
+    import src.gui_2 as gui_2
+
+    source = inspect.getsource(gui_2.App._render_context_composition_panel)
+    assert "context_presets" in source or "preset" in source.lower(), (
+        "Should reference presets"
+    )