feat: DOC-FULL-001 ReadingMaterialRef

Rust 只保存 materialId，不区分 KnowledgeSource/TemporaryFile。

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

crates/zx_document_core/src/lib.rs

@@ -11,5 +11,6 @@ pub mod markdown;
 pub mod material_type;
 pub mod pdf;
 pub mod progress;
+pub mod reading_material;
 pub mod search;
 pub mod text;

crates/zx_document_core/src/reading_material.rs

@@ -0,0 +1,38 @@
+use serde::{Deserialize, Serialize};
+
+/// Reference to a reading material.
+///
+/// Rust does not know whether this is a KnowledgeSource or TemporaryReadingMaterial.
+/// readingTargetType is added by the iOS/API layer.
+#[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize, uniffi::Record)]
+pub struct ReadingMaterialRef {
+    pub material_id: String,
+}
+
+impl ReadingMaterialRef {
+    pub fn new(material_id: impl Into<String>) -> Self {
+        Self {
+            material_id: material_id.into(),
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_new() {
+        let r = ReadingMaterialRef::new("src_123");
+        assert_eq!(r.material_id, "src_123");
+    }
+
+    #[test]
+    fn test_serde() {
+        let r = ReadingMaterialRef::new("src_456");
+        let json = serde_json::to_string(&r).unwrap();
+        assert!(json.contains("src_456"));
+        let back: ReadingMaterialRef = serde_json::from_str(&json).unwrap();
+        assert_eq!(back, r);
+    }
+}

crates/zx_document_ffi/src/lib.rs

@@ -11,6 +11,7 @@ pub use zx_document_core::search::SearchResult;
 pub use zx_document_core::anchors::NoteAnchor;
 pub use zx_document_core::progress::ReadingPosition;
 pub use zx_document_core::events::ReadingEvent;
+pub use zx_document_core::reading_material::ReadingMaterialRef;
 
 use zx_document_core::blocks as core_blocks;