fix(conformance): require successful list to certify deletion

[elezar]

Summary

Require a successful, fully parsed openshell sandbox list traversal before the lifecycle conformance scenario certifies sandbox deletion. This isolates the deletion check currently bundled into #3768 and #3769 so command, authentication, gateway, transport, parse, and pagination failures cannot produce a false pass.

Related Issue

No issue required: this is an obvious localized false-positive fix in the conformance harness.

Follow-up: #3944 proposes a first-class, identity-aware CLI deletion wait so callers do not need to implement this list-based workaround.

Changes

• Replace the nonzero sandbox get deletion signal with a paginated sandbox list search.
• Capture the original sandbox ID before deletion and search for that identity, so a same-name replacement does not keep the wait alive.
• Bound each complete pagination observation by a shared deadline and reject repeated page tokens.
• Treat failed commands, transport errors, malformed JSON, and incomplete pagination as pending observations rather than proof of deletion.

Testing

• cargo fmt --check -- crates/openshell-conformance/src/scenarios/sandbox_lifecycle.rs
• cargo test -p openshell-conformance (18 passed)
• E2E tests added/updated (not applicable; this PR changes the conformance scenario itself)

Checklist

• Follows Conventional Commits
• Commits are signed off (DCO)
• Architecture docs updated (not applicable; no architecture change)

[github-actions]

Label test:e2e applied for 2045004. Open the existing run and click Re-run all jobs to execute with the label set. The run will execute the standard E2E suite after building the required gateway, sandbox, and supervisor images once. The matching required CI gate status on this PR will flip green automatically once the run finishes.