core/agent+cli: reasoning deltas, /stream and /verbose

Decode and stream reasoning_content as ReasoningDeltaEvent; keep it on
assistant messages. CLI shows dim reasoning, toggles stream/verbose, and
prints full tool results when verbose.

tests/test_cli/test_display.py

@@ -0,0 +1,51 @@
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+from plyngent.agent import ReasoningDeltaEvent, TextDeltaEvent, ToolResultEvent
+from plyngent.cli.display import render_events, set_verbose_tool_results
+from plyngent.lmproto.openai_compatible.model import ToolChatMessage
+
+if TYPE_CHECKING:
+    from collections.abc import AsyncIterator
+
+    import pytest
+
+    from plyngent.agent import AgentEvent
+
+
+async def _aiter(events: list[AgentEvent]) -> AsyncIterator[AgentEvent]:
+    for event in events:
+        yield event
+
+
+async def test_render_reasoning_and_text(capsys: pytest.CaptureFixture[str]) -> None:
+    await render_events(
+        _aiter(
+            [
+                ReasoningDeltaEvent(content="think"),
+                TextDeltaEvent(content="hello"),
+            ]
+        )
+    )
+    out = capsys.readouterr().out
+    assert "reasoning: " in out
+    assert "think" in out
+    assert "assistant: " in out
+    assert "hello" in out
+
+
+async def test_tool_result_preview_vs_verbose(capsys: pytest.CaptureFixture[str]) -> None:
+    long = "x" * 200
+    msg = ToolChatMessage(content=long, tool_call_id="1")
+    set_verbose_tool_results(False)
+    await render_events(_aiter([ToolResultEvent(message=msg)]))
+    out = capsys.readouterr().out
+    assert "…" in out
+    assert long not in out
+
+    set_verbose_tool_results(True)
+    await render_events(_aiter([ToolResultEvent(message=msg)]), verbose=True)
+    out2 = capsys.readouterr().out
+    assert long in out2
+    set_verbose_tool_results(False)