Add realtime Yjs collaboration for cloud-linked files

Claude-Session: https://claude.ai/code/session_01PoLmSR1pFVyHf8i5b1rNWk

src-tauri/src/lib.rs

@@ -1062,6 +1062,32 @@ fn cloud_sync_document(
     sync::sync_document(&server_url, &token, &app, &store, &path)
 }
 
+#[tauri::command]
+fn cloud_room_id(
+    app: AppHandle,
+    store: State<'_, Store>,
+    path: String,
+    file: String,
+) -> Result<Option<String>, String> {
+    if let Some(link) = store.document_link(&path)? {
+        return Ok(Some(link.document_id));
+    }
+
+    let meta = store.meta(&path)?;
+    let Some(cloud_project_id) = meta.cloud_project_id else {
+        return Ok(None);
+    };
+
+    let (server_url, token) = cloud_credentials(&app, &store)?;
+    let manifest = sync::get_manifest(&server_url, &token, &cloud_project_id)?;
+
+    Ok(manifest
+        .files
+        .into_iter()
+        .find(|entry| entry.path == file)
+        .map(|entry| format!("project:{}:{}", cloud_project_id, entry.id)))
+}
+
 #[tauri::command]
 fn cloud_resolve_document(
     app: AppHandle,
@@ -1425,6 +1451,7 @@ pub fn run() {
             cloud_download_document,
             cloud_delete_document,
             cloud_sync_document,
+            cloud_room_id,
             cloud_resolve_document,
             cloud_document_link,
             cloud_linked_documents,

src-tauri/src/sync.rs

@@ -241,6 +241,7 @@ pub fn move_cloud_project(
 
 #[derive(Deserialize)]
 pub struct ManifestEntry {
+    pub id: String,
     pub path: String,
     pub hash: String,
 }