refactor(sglang): split remote backend from sidecar launcher

[connorcarpenter15]

Summary

• rename the Rust adapter, crate, library, executable, and engine around the remote-backend abstraction:
  • dynamo-sglang-remote
  • dynamo_sglang_remote
  • SglangRemoteEngine
• compile the remote engine into the Python runtime and expose dynamo._core.backend._run_sglang_remote(argv)
• add dynamo.sglang.sidecar.main(argv) as the actual SGLang-managed sidecar entrypoint
• rename the aggregated and disaggregated launch scripts and update CODEOWNERS

Why

Follow-up to #11408.

The native gRPC adapter is useful as a standalone remote backend and only becomes a sidecar when SGLang manages it together with Dynamo's unified worker lifecycle. Calling the adapter itself a sidecar blurred those two responsibilities, especially for SGLang's --sidecar module contract.

This change keeps transport, discovery, request conversion, health gating, cancellation, and disaggregation in the remote-backend crate. The small Python module owns the SGLang sidecar composition.

Interfaces

Standalone remote backend:

dynamo-sglang-remote --sglang-endpoint http://127.0.0.1:30001

SGLang-managed sidecar:

python3 -m sglang.launch_server \
    <args> \
    --grpc-port 30001 \
    --sidecar dynamo.sglang.sidecar

The native launcher prepends a stable argv[0], releases the GIL, and runs the shared dynamo_backend_common::run worker lifecycle.

Validation

• cargo test -p dynamo-sglang-remote — 21 passed
• cargo test --manifest-path lib/bindings/python/Cargo.toml sglang_remote_argv_prepends_program_name --lib
• cargo fmt --all -- --check
• cargo fmt --manifest-path lib/bindings/python/Cargo.toml -- --check
• Ruff lint and format checks for the changed Python files
• Python bytecode compilation
• bash -n for both renamed launch scripts
• stale-name scan for the removed crate, executable, type, paths, and script names

GPU end-to-end serving and released-wheel installation are left to CI/integration environments.

[github-actions]

🌿 Fern Docs Preview: https://nvidia-preview-019f5dfe-b40f-715d-89c3-c1bc806a5a25.docs.buildwithfern.com/dynamo/dev

[connorcarpenter15]

Superseded by #11636, which uses the internal ai-dynamo/refactor/sglang-remote-backend branch.