fix(orm): resolve MyBatis sources and merge tables by primary key - #1778

MyBatis links could disappear because the writer required class_context, which semantic definitions can omit, and matched short names across packages/repositories. Resolve the XML namespace against unique Java declarations already parsed for this repository, then match each method by its exact source path and name. Ambiguous or unknown namespaces are skipped with a warning instead of guessed.

Native tests also exposed DbTable MERGEs keyed by name even though the schema's primary key is fqn. Correct the MyBatis, annotation-query and ORM-mapping writers, backfill missing datasource values and preserve existing ones. Report submitted mapper records rather than claiming every input became a written edge.

Closes #890. Troubleshooting now explains force reindexing and ambiguous namespace handling.

Validation: 20 focused namespace/Java/native cases pass. Native Kuzu and Ladybug runs execute XML → Java interface → READS/WRITES, same short names in different packages and another repository, missing class_context, unresolved records, pre-existing-table datasource backfill, datasource preservation, annotation-query links and MAPS_TO. The two previous source-string assertions are replaced by these native behavioral checks. Writer regression scope: 63 passed, 1 skipped. Full local unit suite: 1,698 passed, 8 skipped. New code/tests pass Ruff F/E9 and git diff --check. Full CI must pass before merge. No license changes.