feat(adapters): from_jsonschema single-endpoint adapter + shared forwarding core
- src/adapters/forward.rs: shared HTTP forwarding core (extracted from
old from_openapi) — HttpServiceConfig/HttpAuthScheme, build_request
with capabilities-based credential injection (no env vars), forward
+ forward_stream (SSE projection), parse_sse_frames
- src/adapters/from_jsonschema.rs: FromJsonSchema OperationAdapter
(ADR-066) — one registration per call, FromJsonSchema provenance
(leaf, Internal default), Sub -> HandlerKind::Stream (text/event-stream)
- adapted to alkcall 0.1.1: OperationType::Sub, alkcall::client
adapter traits
Verified: cargo test (106 lib tests), clippy -D warnings, fmt.