chore: add diagnostic logs for session restore debugging

- Log each buffer's load result (id, path, exists) in BufferManager::LoadBuffers
- Log workspace buffer filter results in WorkspaceManager::LoadWorkspaces

Co-Authored-By: Le Tan <tamlokveer@gmail.com>

Author: tamlok

src/core/buffer_manager.cpp

@@ -36,6 +36,9 @@ void BufferManager::LoadBuffers() {
   }
 
   for (const auto &record : session_config.buffers) {
+    VXCORE_LOG_INFO("LoadBuffers: processing record id=%s, notebook_id=%s, file_path=%s",
+                    record.id.c_str(), record.notebook_id.c_str(), record.file_path.c_str());
+
     // Resolve notebook pointer if notebook_id is not empty
     Notebook *notebook = nullptr;
     if (!record.notebook_id.empty()) {
@@ -55,7 +58,11 @@ void BufferManager::LoadBuffers() {
       full_path = record.file_path;
     }
 
-    if (!std::filesystem::exists(full_path)) {
+    bool exists = std::filesystem::exists(full_path);
+    VXCORE_LOG_INFO("LoadBuffers: id=%s, full_path=%s, exists=%d",
+                    record.id.c_str(), full_path.c_str(), exists ? 1 : 0);
+
+    if (!exists) {
       VXCORE_LOG_WARN("Skipping buffer: file not found on disk: %s", full_path.c_str());
       continue;
     }

src/core/workspace_manager.cpp

@@ -42,7 +42,10 @@ void WorkspaceManager::LoadWorkspaces() {
     // Filter buffer_ids to only include IDs that exist in BufferManager
     if (buffer_manager_) {
       for (const auto &buf_id : record.buffer_ids) {
-        if (buffer_manager_->GetBuffer(buf_id) != nullptr) {
+        bool found = (buffer_manager_->GetBuffer(buf_id) != nullptr);
+        VXCORE_LOG_INFO("LoadWorkspaces: ws='%s' checking buffer '%s': found=%d",
+                        record.name.c_str(), buf_id.c_str(), found ? 1 : 0);
+        if (found) {
           workspace->buffer_ids.push_back(buf_id);
         } else {
           VXCORE_LOG_WARN("Workspace '%s': skipping missing buffer: %s", record.name.c_str(),