Add a test to validate that redeployment will clean up corrupt node metadata

[shangyian]

Summary

This just adds a test to verify that we create the right NodeRelationship rows on redeploy.

_create_node_revision derives parent links from node_graph (AST scan) and writes them into NodeRelationship, but there was no test confirming this actually happens. This test covers the scenario that motivated recent deployment work: corrupt or missing NodeRelationship rows are healed by a force-redeploy, because each new revision gets its parent links set directly by _create_node_revision, independent of any pre-existing state.

The test deploys a source + transform, deletes the transform's NodeRelationship row to simulate corruption, then force-redeploys and asserts the new revision has exactly one parent link.

Test Plan

• PR has an associated issue: #
• make check passes
• make test shows 100% unit test coverage

Deployment Plan

[netlify]

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