Add SQLite WAL mode files to .gitignore

Add test/test_db-shm and test/test_db-wal to .gitignore to exclude
SQLite Write-Ahead Logging (WAL) mode files that are created during
test execution.

These files are temporary database files created by SQLite when WAL
mode is enabled and should not be tracked in version control.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: takaokouji

.gitignore

@@ -21,5 +21,7 @@ test/log
 log/*.log
 test_db
 test_db-journal
+test/test_db-shm
+test/test_db-wal
 .idea
 *.iml