v2: Local/embedded client mode

[oss-amikos]

Context

The Go client supports a local/embedded mode that runs Chroma in-process without requiring a separate server. The Java client has no equivalent.

Go client modes

Mode	Description
Embedded	Runs Chroma in-process via a Rust shim (chroma-go-local). No network calls.
Server	Starts a local HTTP server in-process and delegates to the HTTP client.

Both modes support persistence to disk.

Suggested Java API

Client client = ChromaClient.local()
    .persistDirectory(Path.of("/data/chroma"))
    .build();

Implementation considerations

• Would require JNI/JNA bindings to the Chroma Rust core, or a shim similar to chroma-go-local
• Alternative: bundle a Chroma server binary and manage its lifecycle
• This is likely a large effort — may be better suited for a separate library/module
• Could leverage TestContainers approach for dev/test scenarios as an interim

Reference

• Go client: NewLocalClient(opts ...LocalClientOption) (*LocalClient, error)
• Go runtime modes: LocalRuntimeModeEmbedded, LocalRuntimeModeServer