Function eval_task_image 

pub fn eval_task_image(
    registry: &str,
    benchmark: &str,
    task_id: &str,
    agent: &str,
    tag: &str,
) -> String

{registry}/evals/<benchmark>-<task>--<agent>:<tag> — the combined eval image for a per-task benchmark (each task bakes a separate image; the task id is part of the name, mirroring benchmark_task_image). Every surface (build / compose / container / job) MUST address per-task evals by this name (benchmarks/RULES.md — eval-image naming). The task id is lowercased for the same Docker-tag reason as benchmark_task_image.