✨ feat: add overlayfs sandbox mode

[zrr1999]

Summary:

• Add opt-in :run(sandbox=overlay) execution using overlayfs.
• Support sandbox.upper=tmpfs so overlay upper/work dirs live on tmpfs.
• Thread sandbox settings through scheduler/process manager and document mode params.

Validation:

• cargo fmt --check
• cargo clippy --all-targets --all-features -- -D warnings
• cargo test -p cue-daemon

[cursor]

Stale comment

Risk: high. Cursor Bugbot is not present on this PR. Overlayfs sandbox execution is security-sensitive and exceeds the low-risk approval threshold; human review is required. No additional reviewers assigned (sole collaborator is the PR author).

  

_{Sent by Cursor Approval Agent: Pull Request Approver}

[cursor]

Stale comment

Risk: high. Overlayfs sandbox execution is security-sensitive and exceeds the low-risk approval threshold, so human review is required before approval. Cursor Bugbot is not present on this PR; no additional reviewers were assigned because the sole collaborator is the PR author.

  

_{Sent by Cursor Approval Agent: Pull Request Approver}

[cursor]

Stale comment

Risk: high. Overlayfs sandbox execution is security-sensitive and exceeds the low-risk approval threshold, so human review is required before approval. Cursor Bugbot is not present on this PR; no additional reviewers were assigned because the sole collaborator is the PR author.

  

_{Sent by Cursor Approval Agent: Pull Request Approver}

[cursor]

Stale comment

Risk: high. Overlayfs sandbox execution is security-sensitive and exceeds the low-risk approval threshold, so human review is required before approval. Cursor Bugbot is not present on this PR; no additional reviewers were assigned because the sole collaborator is the PR author.

  

_{Sent by Cursor Approval Agent: Pull Request Approver}

[cursor]

Stale comment

Risk: high. Overlayfs sandbox execution is security-sensitive and exceeds the low-risk approval threshold, so human review is required before approval. Cursor Bugbot is not present on this PR; no additional reviewers were assigned because the sole collaborator is the PR author.

  

_{Sent by Cursor Approval Agent: Pull Request Approver}

[cursor]

Stale comment

Risk: high. Overlayfs sandbox execution is security-sensitive and exceeds the low-risk approval threshold, so human review is required before approval. Cursor Bugbot is not present on this PR; no additional reviewers were assigned because the sole collaborator is the PR author.

  

_{Sent by Cursor Approval Agent: Pull Request Approver}

[cursor]

Stale comment

Risk: high. Overlayfs sandbox execution is security-sensitive and exceeds the low-risk approval threshold, so human review is required before approval. Cursor Bugbot is not present on this PR; no additional reviewers were assigned because the sole collaborator is the PR author.

  

_{Sent by Cursor Approval Agent: Pull Request Approver}

[cursor]

Stale comment

Risk: high. Overlayfs sandbox execution is security-sensitive and exceeds the low-risk approval threshold, so human review is required before approval. Cursor Bugbot is not present on this PR; no additional reviewers were assigned because the sole collaborator is the PR author.

  

_{Sent by Cursor Approval Agent: Pull Request Approver}

[cursor]

Risk: high. Overlayfs sandbox execution is security-sensitive and exceeds the low-risk approval threshold, so human review is required before approval. Cursor Bugbot is not present on this PR; no additional reviewers were assigned because the sole collaborator is the PR author.

  

_{Sent by Cursor Approval Agent: Pull Request Approver}