feat(run-loop): lift the interactive continuation loop — applies to all agents

The previous commit only kept the root agent alive across cycles. But
``interactive`` propagates to children via ``make_child_factory``, and
the legacy harness's continuation loop applied to every interactive
agent in the tree — children also stayed alive after ``agent_finish``,
ready to receive follow-up messages from the parent or siblings.

Lift the demo-loop pattern out of ``entry.run_strix_scan`` into a
shared helper :func:`strix.run_loop.run_with_continuation` and use it
at both call sites:

- ``entry.run_strix_scan`` for the root agent.
- ``tools.agents_graph.tools.create_agent`` for child agents — the
  ``asyncio.create_task(Runner.run(...))`` becomes
  ``asyncio.create_task(run_with_continuation(...))``.

``StrixOrchestrationHooks.on_agent_end`` drops the ``parent_id is None``
constraint — any interactive agent parks instead of finalizing.
Children that crash still finalize so parents stop waiting on them.

Cancellation propagates correctly: ``bus.cancel_descendants`` cancels
the task; ``run_with_continuation``'s ``await bus.wait_for_message``
catches ``CancelledError`` and returns the last result.

Lint at baseline.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

strix/tools/agents_graph/tools.py

@@ -21,11 +21,12 @@ import logging
 import uuid
 from typing import TYPE_CHECKING, Any, Literal
 
-from agents import RunContextWrapper, Runner, function_tool
+from agents import RunContextWrapper, function_tool
 from agents.items import TResponseInputItem
 
 from strix.orchestration.hooks import StrixOrchestrationHooks
 from strix.run_config_factory import make_agent_context, make_run_config
+from strix.run_loop import run_with_continuation
 
 
 if TYPE_CHECKING:
@@ -464,13 +465,16 @@ async def create_agent(
     )
 
     task_handle = asyncio.create_task(
-        Runner.run(
-            child_agent,
-            input=initial_input,
+        run_with_continuation(
+            agent=child_agent,
+            initial_input=initial_input,
             run_config=child_run_config,
             context=child_ctx,
             hooks=StrixOrchestrationHooks(),
             max_turns=int(inner.get("max_turns", 300)),
+            bus=bus,
+            agent_id=child_id,
+            interactive=bool(inner.get("interactive", False)),
         ),
         name=f"agent-{name}-{child_id}",
     )