feat(call/registry): add OperationRegistry::invoke_streaming() returning ResponseStream

Streaming dispatch path for Subscription operations — counterpart to
invoke(). Same visibility + ACL checks (internal → handler_identity,
external → identity), then dispatches to the StreamingHandler. Pre-handler
errors (not-found, forbidden, INVALID_OPERATION_TYPE for non-Subscription
ops) yield a single error ResponseEnvelope via stream::once and end the
stream. Adds 6 unit tests covering dispatch, not-found, wrong-kind,
internal-from-external, ACL denied, and internal-call handler_identity ACL.

Refs ADR-049 §3, §5.

crates/alknet-call/src/registry/registration.rs

@@ -4,7 +4,7 @@ use std::pin::Pin;
 use std::sync::Arc;
 
 use alknet_core::types::Capabilities;
-use futures::stream::Stream;
+use futures::stream::{self, Stream};
 use serde_json::Value;
 
 use super::context::{CompositionAuthority, OperationContext, ScopedPeerEnv};
@@ -156,6 +156,63 @@ impl OperationRegistry {
             ),
         }
     }
+
+    pub fn invoke_streaming(
+        &self,
+        name: &str,
+        input: Value,
+        context: OperationContext,
+    ) -> ResponseStream {
+        let request_id = context.request_id.clone();
+        let name_owned = name.to_string();
+
+        let registration = match self.operations.get(name) {
+            Some(r) => r,
+            None => {
+                return Box::pin(stream::once(async move {
+                    ResponseEnvelope::not_found(request_id, &name_owned)
+                }));
+            }
+        };
+
+        if registration.spec.visibility == Visibility::Internal && !context.internal {
+            return Box::pin(stream::once(async move {
+                ResponseEnvelope::not_found(request_id, &name_owned)
+            }));
+        }
+
+        let acl = &registration.spec.access_control;
+        let identity = if context.internal {
+            context
+                .handler_identity
+                .as_ref()
+                .and_then(|ca| ca.as_identity())
+        } else {
+            context.identity.clone()
+        };
+
+        if let AccessResult::Forbidden(message) = acl.check(identity.as_ref()) {
+            return Box::pin(stream::once(async move {
+                ResponseEnvelope::forbidden(request_id, message)
+            }));
+        }
+
+        let streaming_handler = match &registration.handler {
+            HandlerKind::Stream(h) => Arc::clone(h),
+            HandlerKind::Once(_) => {
+                return Box::pin(stream::once(async move {
+                    ResponseEnvelope::error(
+                        request_id,
+                        CallError::invalid_operation_type(
+                            "invoke_streaming() called on a Query/Mutation op; use invoke()",
+                        ),
+                    )
+                }));
+            }
+        };
+
+        streaming_handler(input, context)
+    }
 }
 
 impl Default for OperationRegistry {
@@ -1006,4 +1063,189 @@ mod tests {
         assert!(!err.retryable);
         assert!(err.details.is_none());
     }
+
+    async fn collect_stream(mut s: ResponseStream) -> Vec<ResponseEnvelope> {
+        use futures::stream::StreamExt;
+        let mut out = Vec::new();
+        while let Some(env) = s.next().await {
+            out.push(env);
+        }
+        out
+    }
+
+    #[tokio::test]
+    async fn invoke_streaming_on_subscription_dispatches_handler_stream() {
+        let mut registry = OperationRegistry::new();
+        registry
+            .register(HandlerRegistration::new(
+                subscription_spec("events/stream"),
+                HandlerKind::Stream(echo_streaming_handler()),
+                OperationProvenance::Local,
+                None,
+                None,
+                Capabilities::new(),
+            ))
+            .unwrap();
+        let ctx = root_context("req-is-1", None, None, false, ScopedPeerEnv::empty());
+        let stream = registry.invoke_streaming("events/stream", serde_json::json!({"v": 7}), ctx);
+        let items = collect_stream(stream).await;
+        assert_eq!(items.len(), 1);
+        assert_eq!(items[0].request_id, "req-is-1");
+        assert_eq!(items[0].result, Ok(serde_json::json!({"v": 7})));
+    }
+
+    #[tokio::test]
+    async fn invoke_streaming_on_unknown_op_yields_single_not_found() {
+        let registry = OperationRegistry::new();
+        let ctx = root_context("req-is-2", None, None, false, ScopedPeerEnv::empty());
+        let stream = registry.invoke_streaming("missing", serde_json::json!({}), ctx);
+        let items = collect_stream(stream).await;
+        assert_eq!(items.len(), 1);
+        match &items[0].result {
+            Err(e) => {
+                assert_eq!(e.code, "NOT_FOUND");
+                assert!(e.message.contains("missing"));
+            }
+            other => panic!("expected NOT_FOUND, got {other:?}"),
+        }
+    }
+
+    #[tokio::test]
+    async fn invoke_streaming_on_query_op_yields_invalid_operation_type() {
+        let mut registry = OperationRegistry::new();
+        registry
+            .register(HandlerRegistration::new(
+                external_spec("echo", AccessControl::default()),
+                HandlerKind::Once(echo_handler()),
+                OperationProvenance::Local,
+                None,
+                None,
+                Capabilities::new(),
+            ))
+            .unwrap();
+        let ctx = root_context("req-is-3", None, None, false, ScopedPeerEnv::empty());
+        let stream = registry.invoke_streaming("echo", serde_json::json!({}), ctx);
+        let items = collect_stream(stream).await;
+        assert_eq!(items.len(), 1);
+        match &items[0].result {
+            Err(e) => assert_eq!(e.code, "INVALID_OPERATION_TYPE"),
+            other => panic!("expected INVALID_OPERATION_TYPE, got {other:?}"),
+        }
+    }
+
+    #[tokio::test]
+    async fn invoke_streaming_internal_op_from_external_yields_not_found() {
+        let mut registry = OperationRegistry::new();
+        registry
+            .register(HandlerRegistration::new(
+                internal_subscription_spec(AccessControl::default()),
+                HandlerKind::Stream(echo_streaming_handler()),
+                OperationProvenance::Local,
+                None,
+                None,
+                Capabilities::new(),
+            ))
+            .unwrap();
+        let ctx = root_context("req-is-4", None, None, false, ScopedPeerEnv::empty());
+        let stream = registry.invoke_streaming("events/stream", serde_json::json!({}), ctx);
+        let items = collect_stream(stream).await;
+        assert_eq!(items.len(), 1);
+        match &items[0].result {
+            Err(e) => {
+                assert_eq!(e.code, "NOT_FOUND");
+                assert!(e.message.contains("events/stream"));
+            }
+            other => panic!("expected NOT_FOUND, got {other:?}"),
+        }
+    }
+
+    #[tokio::test]
+    async fn invoke_streaming_acl_denied_yields_forbidden() {
+        let mut registry = OperationRegistry::new();
+        registry
+            .register(HandlerRegistration::new(
+                subscription_spec_with_acl(AccessControl {
+                    required_scopes: vec!["admin".to_string()],
+                    ..Default::default()
+                }),
+                HandlerKind::Stream(echo_streaming_handler()),
+                OperationProvenance::Local,
+                None,
+                None,
+                Capabilities::new(),
+            ))
+            .unwrap();
+        let ctx = root_context(
+            "req-is-5",
+            Some(identity_with_scopes("caller", &["user"])),
+            None,
+            false,
+            ScopedPeerEnv::empty(),
+        );
+        let stream = registry.invoke_streaming("events/stream", serde_json::json!({}), ctx);
+        let items = collect_stream(stream).await;
+        assert_eq!(items.len(), 1);
+        match &items[0].result {
+            Err(e) => {
+                assert_eq!(e.code, "FORBIDDEN");
+                assert!(e.message.contains("admin"));
+            }
+            other => panic!("expected FORBIDDEN, got {other:?}"),
+        }
+    }
+
+    #[tokio::test]
+    async fn invoke_streaming_internal_call_uses_handler_identity_for_acl() {
+        let mut registry = OperationRegistry::new();
+        let composing_authority = CompositionAuthority::new("agent-chat", ["admin".to_string()]);
+        registry
+            .register(HandlerRegistration::new(
+                internal_subscription_spec(AccessControl {
+                    required_scopes: vec!["admin".to_string()],
+                    ..Default::default()
+                }),
+                HandlerKind::Stream(echo_streaming_handler()),
+                OperationProvenance::Local,
+                None,
+                None,
+                Capabilities::new(),
+            ))
+            .unwrap();
+        let ctx = root_context(
+            "req-is-6",
+            Some(identity_with_scopes("user", &["user"])),
+            Some(composing_authority),
+            true,
+            ScopedPeerEnv::empty(),
+        );
+        let stream = registry.invoke_streaming("events/stream", serde_json::json!({"ok": 1}), ctx);
+        let items = collect_stream(stream).await;
+        assert_eq!(items.len(), 1);
+        assert_eq!(items[0].request_id, "req-is-6");
+        assert_eq!(items[0].result, Ok(serde_json::json!({"ok": 1})));
+    }
+
+    fn subscription_spec_with_acl(acl: AccessControl) -> OperationSpec {
+        OperationSpec::new(
+            "events/stream",
+            OperationType::Subscription,
+            Visibility::External,
+            serde_json::json!({}),
+            serde_json::json!({}),
+            vec![],
+            acl,
+        )
+    }
+
+    fn internal_subscription_spec(acl: AccessControl) -> OperationSpec {
+        OperationSpec::new(
+            "events/stream",
+            OperationType::Subscription,
+            Visibility::Internal,
+            serde_json::json!({}),
+            serde_json::json!({}),
+            vec![],
+            acl,
+        )
+    }
 }