Fix sandbox artifact downloads

[gitUrLifeTogether]

Fix sandbox artifact downloads by:

• guiding generated artifacts to /tmp paths
• binding the development server to 0.0.0.0 for container access

---

Note

Low Risk
Sandbox prompt/download path guidance and dev-server bind address only; no auth or persistence changes.

Overview
Fixes sandbox artifact downloads when the agent runs in a container by steering user-downloadable outputs toward /tmp paths (so paths in sandbox_artifacts match what the download API can read) and binding the development server to 0.0.0.0 so in-sandbox traffic can reach the host API.

Together these address broken downloads where artifacts lived outside the resolvable filesystem or the dev server only listened on localhost.

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Latest commit: 08a698e

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[cursor]

Cursor Bugbot has reviewed your changes using default effort and found 2 potential issues.

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[chiragjn]

@gitUrLifeTogether before I review this PR, can you please explain the issue - in which scenario is file download not working for you?