feat(cli): display model reasoning content during streaming

Add show_reasoning config (default: False) to display model
thinking/reasoning content in the TUI during streaming.  Reasoning
is emitted via a new emit_reasoning hook on AgentHook, gated by the
channels config.  Display uses ✻ prefix with dim italic styling.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tests/cli/test_cli_input.py

@@ -156,17 +156,65 @@ def test_stream_renderer_stop_for_input_stops_spinner():
     # Create renderer with mocked console
     with patch.object(stream_mod, "_make_console", return_value=mock_console):
         renderer = stream_mod.StreamRenderer(show_spinner=True)
-        
+
         # Verify spinner started
         spinner.start.assert_called_once()
-        
+
         # Stop for input
         renderer.stop_for_input()
-        
+
         # Verify spinner stopped
         spinner.stop.assert_called_once()
 
 
+@pytest.mark.asyncio
+async def test_on_end_writes_final_content_to_stdout_after_stopping_live():
+    """on_end should stop Live (transient erases it) then print final content to stdout."""
+    mock_live = MagicMock()
+    mock_console = MagicMock()
+    mock_console.capture.return_value.__enter__ = MagicMock(
+        return_value=MagicMock(get=lambda: "final output\n")
+    )
+    mock_console.capture.return_value.__exit__ = MagicMock(return_value=False)
+
+    with patch.object(stream_mod, "_make_console", return_value=mock_console):
+        renderer = stream_mod.StreamRenderer(show_spinner=False)
+        renderer._live = mock_live
+        renderer._buf = "final output"
+
+        written: list[str] = []
+        with patch("sys.stdout") as mock_stdout:
+            mock_stdout.write = lambda s: written.append(s)
+            mock_stdout.flush = MagicMock()
+            await renderer.on_end()
+
+    mock_live.stop.assert_called_once()
+    assert renderer._live is None
+    assert written == ["final output\n"]
+
+
+@pytest.mark.asyncio
+async def test_on_end_resuming_clears_buffer_and_restarts_spinner():
+    """on_end(resuming=True) should reset state for the next iteration."""
+    spinner = MagicMock()
+    mock_console = MagicMock()
+    mock_console.status.return_value = spinner
+    mock_console.capture.return_value.__enter__ = MagicMock(
+        return_value=MagicMock(get=lambda: "")
+    )
+    mock_console.capture.return_value.__exit__ = MagicMock(return_value=False)
+
+    with patch.object(stream_mod, "_make_console", return_value=mock_console):
+        renderer = stream_mod.StreamRenderer(show_spinner=True)
+        renderer._buf = "some content"
+
+        await renderer.on_end(resuming=True)
+
+    assert renderer._buf == ""
+    # Spinner should have been restarted (start called twice: __init__ + resuming)
+    assert spinner.start.call_count == 2
+
+
 def test_make_console_force_terminal_when_stdout_is_tty():
     """Console should set force_terminal=True when stdout is a TTY (rich output)."""
     import sys