v1: make isolated agentic-judge collect generic task artifacts and honor judge image

[hallerite]

Context

Post-merge review of #2144 found two coupled gaps in AgenticJudgeEnv(share_runtime=False) now on main:

1. AgenticJudgeEnv.run() calls agents.solver.run(task) without retaining the solver runtime, then JudgeTask.from_trace() restores solution.state.artifacts. Only HarborTask.finalize() currently populates that field; an ordinary task using TaskData.artifacts or /logs/artifacts/ reaches the fresh judge box with an empty artifact set.
2. JudgeTask.from_trace() copies solution.task.data.image onto the judge task even in isolated mode. Runtime compilation gives that task image precedence over judge.runtime.image, so a purpose-built judge image is silently replaced by the solver image despite the config contract that the judge runtime is honored when sharing is disabled.

These findings landed on #2152 only because its base branch disappeared after #2144 was squash-merged; they are inherited main behavior, not part of #2152's Harbor diff.

Suggested direction

• In isolated mode, provision the solver runtime explicitly, run the solver in it, and collect task.data.artifacts (including the convention sweep) after task finalization but before leaving the runtime context.
• Pass that collected set to the isolated judge task rather than assuming a task subclass populated transient trace state.
• Do not set the isolated judge task's image from the solver row; let the configured judge runtime image win. Preserve only task-level fields that are intentionally shared.
• Keep shared mode unchanged.

Done when

• A plain Task that writes to /logs/artifacts/ is restored into an isolated judge sandbox.
• Declared artifact paths work without a Harbor-specific finalize() override.
• An explicit judge.runtime.image is the image used in isolated mode.
• Shared mode continues to use the live solver workspace and runtime.