v0.4.0a4

Client/server 0.4.0a4 are published as an opt-in alpha pair. ProviderSandbox lifecycle help now matches the actual canonical parameters; signatures and executable behavior are unchanged. Refs #124, #125.

The existing publication workflow completed SUCCESS on attempt 2. Attempt 1 retained its real post-upload metadata-404 failure; both preserved artifact sets and all four official downloads have identical SHA-256 values. Fresh official installation, imports, corrected async/sync help, local HTTP behavior and owned-process cleanup passed. This does not certify all templates, providers or production workloads.

python -m pip install --index-url https://pypi.org/simple agent-sandbox-client==0.4.0a4
python -m pip check