refactor(reasoning): unify reasoning extraction across providers

Reasoning surfacing was split across three branches in runner.py plus
two separate streaming buffers (loop hook and runner progress stream),
with three independent display-side gates in the CLI. This collapsed
the policy into one source of truth and fixed two real bugs:

- Structured `reasoning_content` was suppressed whenever the answer was
  streamed, because the runner gated emission on `streamed_content`.
  Providers don't stream `reasoning_content`; it only arrives on the
  final response, so the answer stream and the reasoning channel are
  independent. Added `streamed_reasoning` to `AgentHookContext` to track
  the right bit.
- `channels.showReasoning` was subordinated to `sendProgress`. They are
  orthogonal — turning off progress streaming shouldn't silence
  reasoning. Reworked the CLI gates accordingly.

Single-helper consolidation:

- `extract_reasoning(reasoning_content, thinking_blocks, content)`
  returns `(reasoning_text, cleaned_content)` with a defined fallback
  order: dedicated field → Anthropic thinking_blocks → inline
  `<think>`/`<thought>` tags. Models that expose none of these
  short-circuit to `(None, content)` — zero overhead.
- `IncrementalThinkExtractor` replaces the ad-hoc `emit_incremental_think`
  function and its hand-rolled "emitted cursor" state in both the loop
  hook and the runner progress stream.

Also documented the new `showReasoning` channel option in
docs/configuration.md and noted its independence from sendProgress.

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/cli/test_interactive_retry_wait.py

@@ -88,3 +88,26 @@ async def test_non_reasoning_progress_not_affected_by_show_reasoning():
 
     assert handled is True
     assert calls == ["working on it..."]
+
+
+@pytest.mark.asyncio
+async def test_reasoning_shown_when_send_progress_disabled():
+    """Reasoning display is governed by `show_reasoning` alone, independent
+    of `send_progress` — the two knobs are orthogonal."""
+    calls: list[str] = []
+    channels_config = SimpleNamespace(
+        send_progress=False, send_tool_hints=False, show_reasoning=True,
+    )
+    msg = SimpleNamespace(
+        content="Let me think about this...",
+        metadata={"_progress": True, "_reasoning": True},
+    )
+
+    with patch(
+        "nanobot.cli.commands._print_cli_reasoning",
+        side_effect=lambda t, th, r=None: calls.append(t),
+    ):
+        handled = await commands._maybe_print_interactive_progress(msg, None, channels_config)
+
+    assert handled is True
+    assert calls == ["Let me think about this..."]