fix: keep session deletion and rollouts consistent

[superman2003]

Summary

• keep Codex thread row deletion inside the SQLite transaction until rollout files are removed
• restore rollout backups if file deletion or transaction commit fails
• restore files before undoing database rows and remove partial restores when the database transaction fails

Test plan

• cargo fmt --all -- --check
• cargo test -p codex-plus-data --lib storage::tests -- --test-threads=1 (2 passed)
• cargo test -p codex-plus-data --test storage_adapter -j 1 -- --test-threads=1 (19 passed)
• cargo check -p codex-plus-data -j 1

[BigPizzaV3]

Codex++ maintainer review note

当前 main 下这个 PR 仍存在 merge conflict，暂时不能合并。请先 rebase 到最新 main 并解决冲突；更新后我们会重新跑针对性测试再复审。

This PR currently conflicts with main, so it is not mergeable yet. Please rebase onto the latest main and resolve the conflicts, then we can review and test it again.