Fix sub_results iteration in the skills examples

[ling-senpeng13]

sub_results is a dict keyed by agent name rather than object list, so iterating it yields strings. 32_skills_multi_agent.py parallel died on the print — PARALLEL is the strategy that actually populates it:

AttributeError: 'str' object has no attribute 'status'

src/conductor/ai/agents/result.py#L124

    finish_reason: Optional[FinishReason] = None
    error: Optional[str] = None
    events: List["AgentEvent"] = field(default_factory=list)
    sub_results: Dict[str, Any] = field(default_factory=dict)

The other two call sites have the same bug, and survived only because their sub_results was empty.

Verified against a 3.32.0-rc18 server: all 8 modes across both examples complete, and parallel prints all three sub-agent outputs.