feat(lander): integrate persistent insert & get lsm store

lsm/src/store/lsm_store_disk_write.c

@@ -100,6 +100,9 @@ lsm_error lsm_entry_sync(lsm_store *store, lsm_entry_handle *handle) {
     res = lsm_entry_write_uint64_t(store->idx_file, new_block_count);
 
     if (res == lsm_error_ok) {
+      // Only if we successfully updated the on-disk counter do we make the code
+      // aware that the file's size has increased. This way, if a write to the
+      // counter fails, the code will simply reuse the already written content.
       store->idx_file_size += entry_size;
       store->idx_file_block_count = new_block_count;
     }