v0.4.0

Added

• import_chatgpt_file with ChatGPT openai/fileParams binding, bounded HTTPS download, SHA-256 verification, binary SSH streaming, and atomic remote commit.
• export_remote_file with raw SSH streaming, verified local spool, ChatGPT tool-result file references, and MCP HTTPS resource links.
• Short-lived 256-bit artifact capability URLs with download-count limits, HEAD, byte ranges, digest headers, and immutable file metadata.
• Artifact size, concurrency, timeout, host-allowlist, spool, and public-origin configuration.
• Random-binary end-to-end tests for both directions, idempotent retries, conflicting content, checksum rejection, and HTTP download behavior.
• Prometheus execution-duration histogram grouped by final state.
• Maximum-concurrency gauge and lifecycle-log duration metadata for operational dashboards.

Changed

• Retained base64 upload_file and download_file as small-file compatibility tools rather than the primary artifact path.
• Generalized SSH process spawning so binary stdin/stdout transfers preserve backpressure.

Security

• Remote artifact writes now use same-directory temporary files, fsync, SHA-256 validation, and atomic commit.
• Identical retries are idempotent; existing files with different content require explicit overwrite.
• Documented the separate public /artifacts/ data-plane boundary required when Secure MCP Tunnel keeps MCP JSON-RPC private.