2b8c962: Add a RustFS adapter (files-sdk/rustfs). RustFS is the Apache-2.0 Rust object store that runs as a MinIO drop-in, and rustfs() mirrors the minio() adapter one-to-one: path-style addressing on by default (virtual-hosted needs RUSTFS_SERVER_DOMAINS), the us-east-1 signing region matching the server’s RUSTFS_REGION default, "RustFS error" provider labels, and the same client: "aws-sdk" | "fetch" engine choice with the @aws-sdk-free fetch engine defaulting on inside Cloudflare Workers. Credentials fall back to RUSTFS_ACCESS_KEY_ID / RUSTFS_SECRET_ACCESS_KEY, then to the RUSTFS_ACCESS_KEY / RUSTFS_SECRET_KEY names the server itself reads so one docker-compose .env configures both sides. Available to the CLI and MCP server as --provider rustfs.