fix(proof-harvest): no proxy tar leak on missing holdout shard

[echobt]

Summary

CI on main (#235 / 8b39d24f) failed tests::missing_holdout_shard_does_not_leak_a_proxy_tar while the sibling live_extras_holdout_refuse_does_not_leak_a_proxy_tar passed.

Holdout-first packing in live_extras is already correct: a missing/mismatched shard returns HoldoutStoreMissing before pack_proxy_tar_to, so that refuse path does not create a proxy tar. The CI failure was a leftover-scan race: leak tests listed /tmp/proof-proxy-{pid}-*.tar, and a concurrent unit test (pack_helpers_succeed_on_operator_staged_trees / a live score() pack) still held a tar in the same process temp dir.

This PR:

• Stages leak-test proxy tars into an isolated per-test directory and scans only that dir.
• Names proxy tars with a process-wide sequence so concurrent harvests cannot clobber the same /tmp path.
• Adds a guard test that a successful live_extras writes into the configured dir and ProxyTarGuard deletes it on drop.

Does not change StubWin, FORCE_SIM, pins, overlays, or eval digests.

Greptile

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Test plan

• cargo test -p proof-harvest --lib (both leak tests + guard test; 10 repeats of the leak tests)
• cargo clippy -p proof-harvest --all-targets -- -D warnings
• cargo run -p xtask -- loc-cap
• cargo fmt --all -- --check (formatted proof-harvest; workspace fmt not re-run)

Risk

Test isolation + unique tar names on the harvest control plane only. No deploy, miner CVM, signature domain, or emission impact.

Naming

I did not rename BASE_* environment variables, deployed host paths
(/opt/base, /run/base, …), GHCR baseintelligence/base package names, or
base-*-v1 cryptographic domain tags, unless this PR’s purpose is a coordinated
cutover documented in docs/NAMING.md.

  

[greptile-apps]

Greptile Summary

Summary

• Proxy-tar staging is isolated for concurrent test execution.
• Generated proxy-tar filenames include a process-wide sequence to avoid same-process collisions.
• Leak checks and cleanup coverage use dedicated staging directories.

Confidence Score: 5/5

Safe to merge.

There are no outstanding findings.

_{Reviews (2): Last reviewed commit: "fix(proof-harvest): case-insensitive lef..." | Re-trigger Greptile}

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