Function audit_skill_invocation 

pub fn audit_skill_invocation(
    skill_id: &str,
    entry_point: &str,
    cwd: &str,
    input_json: &str,
    output: &str,
    exit_code: i32,
    duration_ms: u64,
)

Audit: skill_invocation (P0 可观测 - 记录谁在什么上下文调用了哪个 Skill、输入摘要、输出摘要)