What changed

• expose runtime-scoped image handles across the Python, Node, Go, and C SDKs
• enforce runtime shutdown and free liveness for FFI image handles and cached SDK image handles
• restore external Go module consumers by installing both libboxlite.a and include/boxlite.h into the module cache
• make the FFI rest dependency test-only, document the current Go context.Context cancellation limitation, and cache image handles in Node/Python instead of re-fetching them per call
• add regression coverage for Go setup, runtime shutdown/free image-handle behavior, and SDK wrapper behavior

Why

The SDKs needed parity with the core runtime image APIs, but the initial rollout had two real follow-up issues:

• Go module consumers outside a full repo checkout could no longer find boxlite.h
• FFI image handles could continue operating past the runtime shutdown/free boundary

This update keeps the SDK image-handle API, fixes the Go module packaging path, and makes the shutdown contract explicit across the FFI and language bindings.

Impact

• SDK users can call runtime.images.pull(...) and runtime.images.list() consistently across Python, Node, Go, and C
• Go consumers using go get github.com/boxlite-ai/boxlite/sdks/go can build from the published module cache again
• image handles now reject operations after runtime shutdown/free instead of continuing through a stale execution path
• Node/Python wrappers no longer pay redundant runtime.images() setup cost on every call

Root cause

• The Go prebuilt path assumed a full repository checkout after moving the header out of sdks/go
• the FFI image-handle path owned enough runtime state to stay usable after shutdown unless it checked liveness explicitly
• the wrapper SDKs mirrored the older per-call runtime-image lookup instead of caching the handle once

Validation

• cargo fmt --all
• git diff --check
• cargo test -p boxlite-ffi
• cargo clippy -p boxlite-ffi --tests -- -D warnings
• cargo check -p boxlite-node -p boxlite-python
• cd sdks/go && go test ./cmd/setup
• pre-push make test hook for changed components (c ffi go node python rust)