fix(sdk): populate RunResult.tools_used and RunResult.messages

``Nanobot.run()`` has always documented ``RunResult.tools_used`` and
``RunResult.messages`` but actually returned ``[]`` for both, so SDK
consumers could never inspect which tools fired or what the final
message list looked like — the only useful field was ``content``.

This threads the data out via a tiny ``_SDKCaptureHook`` that installs
alongside any user-supplied hooks. The capture hook accumulates tool
names across iterations and snapshots the message list on each
``after_iteration`` call; the last snapshot reflects end-of-turn state.

Only the SDK facade is touched: ``AgentLoop.process_direct`` and
``AgentRunner`` signatures are unchanged, so channels / CLI / API paths
are unaffected.

nanobot/nanobot.py

@@ -6,7 +6,7 @@ from dataclasses import dataclass
 from pathlib import Path
 from typing import Any
 
-from nanobot.agent.hook import AgentHook
+from nanobot.agent.hook import AgentHook, AgentHookContext
 from nanobot.agent.loop import AgentLoop
 from nanobot.bus.queue import MessageBus
 
@@ -104,9 +104,10 @@ class Nanobot:
                 Different keys get independent history.
             hooks: Optional lifecycle hooks for this run.
         """
+        capture = _SDKCaptureHook()
         prev = self._loop._extra_hooks
-        if hooks is not None:
-            self._loop._extra_hooks = list(hooks)
+        base_hooks = list(hooks) if hooks is not None else list(prev or [])
+        self._loop._extra_hooks = [capture, *base_hooks]
         try:
             response = await self._loop.process_direct(
                 message, session_key=session_key,
@@ -115,7 +116,30 @@ class Nanobot:
             self._loop._extra_hooks = prev
 
         content = (response.content if response else None) or ""
-        return RunResult(content=content, tools_used=[], messages=[])
+        return RunResult(
+            content=content,
+            tools_used=capture.tools_used,
+            messages=capture.messages,
+        )
+
+
+class _SDKCaptureHook(AgentHook):
+    """Record tool names and the final message list for ``RunResult``.
+
+    The runner mutates ``context.messages`` in place across iterations, so the
+    snapshot is refreshed on every ``after_iteration`` call; the last call
+    reflects the end-of-turn state the SDK caller cares about.
+    """
+
+    def __init__(self) -> None:
+        super().__init__()
+        self.tools_used: list[str] = []
+        self.messages: list[dict[str, Any]] = []
+
+    async def after_iteration(self, context: AgentHookContext) -> None:
+        for call in context.tool_calls:
+            self.tools_used.append(call.name)
+        self.messages = list(context.messages)
 
 
 def _make_provider(config: Any) -> Any: