TypeScript custom HTTP transport

new GitStorage({ name, key, fetch }) (also CodeStorage and createClient) accepts an optional fetch: typeof globalThis.fetch. It applies to all SDK HTTP calls, including repository handles, downloads, and streaming commit uploads. The default is global fetch; the SDK adds no automatic retries. Callers own retry limits, backoff, cancellation, and safe body replay. Do not blindly retry writes or reuse consumed streaming request bodies. This option does not affect Git CLI traffic. See packages/code-storage-typescript/README.md for a read-only retry example. Python and Go do not use this TypeScript option.