feat(conductor): inherit model selection when spawning subagents

[Kailigithub]

Summary

Subagents spawned by the conductor now inherit the conductor agent's current model selection instead of always defaulting to model index 0.

Problem

When the user switches models via /llms in the conductor session, spawned subagents still used model 0 (the default). This causes inconsistency between the conductor and subagent capabilities, costs, and fallback strategies.

Solution

Added a 3-line check in start_subagent(): if the conductor agent is initialized, call agent.next_llm(conductor_agent.llm_no) on the new subagent before starting its runner thread.

The guard if conductor_agent is not None ensures backward compatibility — if subagents are created before the conductor agent is ready, they still fall back to model 0.

Testing

• python3 -m py_compile frontends/conductor.py — passes
• Behavior verified: conductor_agent.llm_no is an integer attribute on GenericAgent instances, next_llm() accepts integers

Closes #456

[Kailigithub]

Closing this PR — it's been CONFLICTING for 44 days with no review activity, and I don't want to leave stale work in the queue. The underlying change (subagent model inheritance via start_subagent()) is small and well-scoped; happy to reopen on a fresh branch rebased onto current main if the change is still wanted, otherwise the diff is preserved locally on branch feat/issue-456-subagent-model-inherit and can be cherry-picked at any time.