ocs_doc_api: Phase 2b-a (Text/MText annotations)

- CreateText/CreateMText/SetTextContent ops + GetTextContent query (append-only).
- backend add_text/add_mtext/set_text_content/text_content (Text.value/MText.value).
- facade create_text/create_mtext + Text/MText handles with content()/set_content().
- Text/MText coarse bounds + transform (insertion point); ensure_transformable.
- spec Text/MText families; api_reference + binding_schema regenerated; mocks.
- can_modify backend hook (exists + not-locked) for SetTextContent validation.
- consistency baseline extended with the appended variants.
- Test phase2b_text_mtext_create_content_transform -> 605 host lib + 3 consistency green.

crates/ocs_doc_api/tests/mock_backend.rs

@@ -21,6 +21,8 @@ struct MockBackend {
     undo_steps: u32,
     bodies: HashMap<ObjectId, KernelBody>,
     kinds: HashMap<ObjectId, String>,
+    /// Stored text content for Text/MText annotations.
+    text_values: HashMap<ObjectId, String>,
 }
 
 impl MockBackend {
@@ -73,6 +75,27 @@ impl DocApiBackend for MockBackend {
     fn add_viewport(&mut self, _spec: &ocs_doc_api::ops::ViewportSpec) -> ApiResult<ObjectId> {
         Ok(self.alloc("Viewport"))
     }
+    fn add_text(&mut self, spec: &ocs_doc_api::ops::TextSpec) -> ApiResult<ObjectId> {
+        let id = self.alloc("Text");
+        self.text_values.insert(id, spec.value.clone());
+        Ok(id)
+    }
+    fn add_mtext(&mut self, spec: &ocs_doc_api::ops::MTextSpec) -> ApiResult<ObjectId> {
+        let id = self.alloc("MText");
+        self.text_values.insert(id, spec.value.clone());
+        Ok(id)
+    }
+    fn set_text_content(&mut self, id: ObjectId, value: &str) -> ApiResult<()> {
+        if let std::collections::hash_map::Entry::Occupied(mut e) = self.text_values.entry(id) {
+            e.insert(value.to_string());
+            Ok(())
+        } else {
+            Err(ApiError::UnknownId(id))
+        }
+    }
+    fn text_content(&self, id: ObjectId) -> ApiResult<String> {
+        self.text_values.get(&id).cloned().ok_or(ApiError::UnknownId(id))
+    }
     fn add_vertex(&mut self, id: ObjectId, _at: usize, _point: [f64; 3]) -> ApiResult<()> {
         if self.entity_exists(id) {
             Ok(())

crates/ocs_doc_api/tests/spec_wire_consistency.rs

@@ -53,6 +53,9 @@ fn operation_variants() -> Vec<String> {
         Operation::DeleteMany(vec![]),
         Operation::CreateInsert(InsertSpec { block_name: String::new(), insert_point: [0.0; 3], scale: 1.0, rotation: 0.0 }),
         Operation::CreateViewport(ViewportSpec { center: [0.0; 3], width: 0.0, height: 0.0, view_target: [0.0; 3], view_height: 0.0 }),
+        Operation::CreateText(ocs_doc_api::ops::TextSpec { value: String::new(), insertion_point: [0.0; 3], height: 0.0, rotation: 0.0 }),
+        Operation::CreateMText(ocs_doc_api::ops::MTextSpec { value: String::new(), insertion_point: [0.0; 3], height: 0.0 }),
+        Operation::SetTextContent { id: ObjectId::from_u64(0), value: String::new() },
     ];
     // Derive the variant names by serializing a probe of each and reading the
     // bincode variant index -> name map is not available; instead match by
@@ -77,6 +80,7 @@ fn query_variants() -> Vec<String> {
         Query::GetVolume { id: ObjectId::from_u64(0) },
         Query::GetIntersects { a: ObjectId::from_u64(0), b: ObjectId::from_u64(0) },
         Query::GetGeometryRevision,
+        Query::GetTextContent { id: ObjectId::from_u64(0) },
     ];
     marker
         .iter()
@@ -127,6 +131,9 @@ const OPERATION_BASELINE: &[&str] = &[
     "DeleteMany",
     "CreateInsert",
     "CreateViewport",
+    "CreateText",
+    "CreateMText",
+    "SetTextContent",
 ];
 
 /// Recorded baseline of the `Query` variant order.
@@ -137,6 +144,7 @@ const QUERY_BASELINE: &[&str] = &[
     "GetVolume",
     "GetIntersects",
     "GetGeometryRevision",
+    "GetTextContent",
 ];
 
 #[test]