fix(gui): use imscope.child for comms_scroll (was inside conditional, leaving child open)

ROOT CAUSE: render_comms_history_panel had imgui.end_child() nested INSIDE
an 'if app._scroll_comms_to_bottom:' block at line 3758. When
_scroll_comms_to_bottom was False (the common case), end_child was
NOT called, leaving the comms_scroll child window open. This caused
the imGui state to corrupt: tab_item.end_tab_item, tab_bar.end_tab_bar,
and the outer window.end all saw that the child was still open
(WithinEndChildID was set), triggering 'Must call EndChild() and not
End()!' assertion.

FIX: Convert the entire comms_scroll block to imscope.child (which uses
Python's with statement for exception-safe end_child). The scroll-to-bottom
logic is now correctly nested INSIDE the with block, and there's no
manual end_child to forget.

Tests:
- Updated test_comms_scroll_no_clipping.py to check imscope.child
  instead of begin_child
- 28/28 broad regression pass

src/gui_2.py

@@ -3676,7 +3676,7 @@ def render_comms_history_panel(app: App) -> None:
  imgui.separator()
 
  avail = imgui.get_content_region_avail()
- imgui.begin_child("comms_scroll", imgui.ImVec2(avail.x, avail.y), False, imgui.WindowFlags_.horizontal_scrollbar)
+ with imscope.child("comms_scroll", imgui.ImVec2(avail.x, avail.y), imgui.WindowFlags_.horizontal_scrollbar):
   log_to_render = app._comms_log_cache
   
   for i, entry in enumerate(log_to_render):
@@ -3748,7 +3748,6 @@ def render_comms_history_panel(app: App) -> None:
    elif kind == "tool_call":   render_heavy_text(app, payload.get("name", "call"), payload.get("script") or json.dumps(payload.get("args", {}), indent=1), idx_str)
    elif kind == "tool_result": render_heavy_text(app, payload.get("name", "result"), payload.get("output", ""), idx_str)
    else:                       render_heavy_text(app, "data", str(payload), idx_str)
-
    imgui.separator()
    imgui.pop_id()
 
@@ -3756,7 +3755,6 @@ def render_comms_history_panel(app: App) -> None:
    imgui.set_scroll_here_y(1.0)
    app._scroll_comms_to_bottom = False
 
-  imgui.end_child()
  if app.perf_profiling_enabled: app.perf_monitor.end_component("_render_comms_history_panel")
 
 def render_takes_panel(app: App) -> None:

tests/test_comms_scroll_no_clipping.py

@@ -18,8 +18,10 @@ def test_comms_history_renders_all_entries_not_just_early_subset(app_instance):
   mock_imgui.push_style_color = MagicMock()
   mock_imgui.pop_style_color = MagicMock()
   mock_imgui.set_scroll_here_y = MagicMock()
-  mock_imgui.get_content_region_avail = MagicMock(return_value=MagicMock(x=800.0, y=600.0))
+  mock_imgui.get_content_region_avail = MagicMock(return_value=type("P", (), {"x": 800.0, "y": 600.0})())
-  mock_imgui.ImVec2 = lambda *a: ("ImVec2", a)
+  def _imvec2(x, y=0):
+   m = MagicMock(); m.x = float(x); m.y = float(y); return m
+  mock_imgui.ImVec2 = _imvec2
   mock_imgui.ImVec4 = lambda *a: ("ImVec4", a)
   mock_imscope.child = MagicMock()
   mock_imscope.child.return_value.__enter__ = MagicMock()
@@ -35,14 +37,14 @@ def test_comms_history_renders_all_entries_not_just_early_subset(app_instance):
   except Exception as e:
    import pytest
    pytest.fail(f"render_comms_history_panel raised: {e}")
- comms_calls = [call for call in mock_imgui.begin_child.call_args_list if call[0][0] == "comms_scroll"]
+  comms_calls = [call for call in mock_imscope.child.call_args_list if call[0][0] == "comms_scroll"]
   assert len(comms_calls) == 1, "comms_scroll child should be opened once"
- comms_call = next((c for c in mock_imgui.begin_child.call_args_list if c[0][0] == "comms_scroll"), None)
+  comms_call = comms_calls[0]
- assert comms_call is not None, "comms_scroll child should be among begin_child calls"
   args, _ = comms_call
- size_arg = args[1]
+  size_arg = args[1] if len(args) > 1 else 0
- if isinstance(size_arg, tuple) and len(size_arg) == 2 and isinstance(size_arg[0], str):
+  if hasattr(size_arg, 'x'):
-  actual = size_arg[1]
+   size_x, size_y = size_arg.x, size_arg.y
   else:
-  actual = size_arg
+   size_x = size_arg
- assert actual != (0, 0), f"comms_scroll child should use explicit content region size, got {actual}"
+   size_y = 0
+  assert size_x > 0 and size_y > 0, f"comms_scroll child should use explicit content region size, got ({size_x}, {size_y})"