Adds ``deerflow.community.e2b_sandbox.E2BSandboxProvider`` with parity
to AioSandboxProvider: metadata-keyed per-thread persistence, server-
side idle timeout, warm-pool reclaim with liveness checks, /mnt/user-data
bootstrap symlinks, dead-sandbox auto-rebuild, and release-time mirror
of agent outputs back to the host artifact directory.
Signed-off-by: joey <zchengjoey@gmail.com>