fix(studio): make assignments undoable and retain effect controls

crates/hypercolor-daemon/src/api/openapi.rs

@@ -1,7 +1,7 @@
 #![allow(clippy::needless_for_each)]
 
 use axum::routing::MethodRouter;
-use utoipa::openapi::path::{OperationBuilder, ParameterBuilder, ParameterIn, Paths};
+use utoipa::openapi::path::{OperationBuilder, Parameter, ParameterBuilder, ParameterIn, Paths};
 use utoipa::openapi::request_body::RequestBodyBuilder;
 use utoipa::openapi::schema::{ObjectBuilder, Schema, Type};
 use utoipa::openapi::security::{HttpAuthScheme, HttpBuilder, SecurityScheme};
@@ -123,6 +123,7 @@ pub(crate) struct OperationDoc {
     request_schema: Option<SchemaRegistrar>,
     additional_schemas: Vec<SchemaRegistrar>,
     query: Option<ParameterProvider>,
+    headers: Vec<Parameter>,
 }
 
 impl OperationDoc {
@@ -207,6 +208,7 @@ impl OperationDoc {
             request_schema: None,
             additional_schemas: Vec::new(),
             query: None,
+            headers: Vec::new(),
         }
     }
 
@@ -255,6 +257,19 @@ impl OperationDoc {
         self
     }
 
+    pub(crate) fn required_header(mut self, name: &'static str, description: &'static str) -> Self {
+        self.headers.push(
+            ParameterBuilder::new()
+                .name(name)
+                .parameter_in(ParameterIn::Header)
+                .required(Required::True)
+                .description(Some(description))
+                .schema(Some(ObjectBuilder::new().schema_type(Type::String)))
+                .build(),
+        );
+        self
+    }
+
     pub(crate) fn component<T: utoipa::ToSchema>(mut self) -> Self {
         self.additional_schemas.push(register_schema::<T>);
         self
@@ -320,6 +335,9 @@ fn operation(path: &str, document: OperationDoc) -> utoipa::openapi::path::Opera
             builder = builder.parameter(parameter);
         }
     }
+    for header in document.headers {
+        builder = builder.parameter(header);
+    }
 
     if let Some((schema, required)) = document.request {
         builder = builder.request_body(Some(

crates/hypercolor-daemon/src/api/routes/scene.rs

@@ -96,6 +96,22 @@ pub(super) fn router() -> OpenApiRouter<Arc<AppState>> {
                 .body::<hypercolor_types::api::scene::ZoneLayoutRequest>(),
             ],
         ))
+        .routes(openapi::documented_route(
+            "/scene/members/edit",
+            axum::routing::post(scene::edit_members),
+            [
+                OperationDoc::post::<hypercolor_types::api::scene::EditMembersResponse>(
+                    "edit_live_scene_members",
+                    "scenes",
+                    "Atomically edit live scene memberships",
+                )
+                .body::<hypercolor_types::api::scene::EditMembersRequest>()
+                .required_header(
+                    "If-Match",
+                    "Last observed scene revision, as a quoted or bare integer. The wildcard * is not accepted.",
+                ),
+            ],
+        ))
         .routes(openapi::documented_route(
             "/scene/zones/{zone}/members",
             axum::routing::post(scene::assign_members),

crates/hypercolor-daemon/src/api/scene.rs

@@ -318,6 +318,29 @@ pub async fn unassign_member(
 
 // ── Layers ───────────────────────────────────────────────────────────────
 
+/// `POST /api/v1/scene/members/edit` applies a reversible membership transaction.
+pub async fn edit_members(
+    State(state): State<Arc<AppState>>,
+    headers: HeaderMap,
+    Json(body): Json<hypercolor_types::api::scene::EditMembersRequest>,
+) -> Response {
+    let expected = match parse_if_match(&headers) {
+        Ok(Some(expected)) => expected,
+        Ok(None) => {
+            return DomainError::validation("If-Match is required for membership edits")
+                .into_response();
+        }
+        Err(error) => return error.into_response(),
+    };
+    match scene_tree::edit_members(&state.domains.scene_tree, body, expected).await {
+        Ok(outcome) => {
+            let revision = outcome.document.revision;
+            with_revision(envelope::ok(outcome), revision)
+        }
+        Err(error) => error.into_response(),
+    }
+}
+
 /// `GET /api/v1/scene/zones/{zone}/layers` — the zone's stack.
 pub async fn list_layers(State(state): State<Arc<AppState>>, Path(zone): Path<String>) -> Response {
     let zone_id = match parse_zone_id(&zone) {

crates/hypercolor-daemon/src/domain/layout.rs

@@ -996,7 +996,7 @@ pub(crate) fn validate_layout_sampling_radii(layout: &SpatialLayout) -> Result<(
     Ok(())
 }
 
-fn validate_output_sampling_radii(output: &Output) -> Result<(), DomainError> {
+pub(crate) fn validate_output_sampling_radii(output: &Output) -> Result<(), DomainError> {
     validate_output_sampling_radii_text(output).map_err(DomainError::validation)
 }
 

crates/hypercolor-daemon/src/domain/scene_tree.rs

@@ -37,6 +37,9 @@ use crate::domain::output::OutputContext;
 use crate::domain::scene::SceneMutation;
 use crate::domain::{DomainError, DomainErrorDetails, MutationContext, ResourceKind};
 
+mod member_edits;
+pub use member_edits::edit_members;
+
 /// Live scene-tree authority shared by REST and MCP adapters.
 #[derive(Clone)]
 pub struct SceneTreeContext {