* fix(sandbox): bound remaining shell session cleanup requests
release_command_scope(), close()'s scoped-session drain, and close()'s recovery-session cleanup called shell.cleanup_session() without a request budget, so a stalled cleanup could hold the thread-key serializer, scoped.lock, or the sandbox lock for the SDK's default transport budget. Pass the existing _bounded_cleanup_request_options() (5s, max_retries=0) at those three sites; _cleanup_session_best_effort() and its swallow-and-log contract are unchanged, as are create_session and list_dir lifetimes.
* fix(sandbox): bound AIO list_dir with a directory deadline
Give AioSandbox.list_dir its own 60s directory deadline with a 65s no-retry
host envelope, independent of bash_command_timeout. Preserve #5634's
shell-generation selection: list_dir runs on the current recovery session once
the implicit shell is fenced, and an ambiguous list_dir outcome - transport
timeout or an ambiguous returned status - fences whichever generation actually
executed the request, dropping local recovery ownership and attempting bounded
best-effort cleanup instead of leaving that session reusable. hard_timeout
remains definite termination and keeps the targeted session reusable. Only
completed/None results are parsed, so a partial find is never returned as a
complete listing.
Session creation RPC lifetime remains out of scope.
* fix(sandbox): recover sessions after transport failures
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Co-authored-by: Willem Jiang <willem.jiang@gmail.com>