fix(neo4j): reconcile removed application artifacts

[MikeeI]

Summary

Remove artifact subtrees that disappeared from a full application analysis.
Keep neutral artifacts owned by sibling analyzers and shared package nodes intact.

Evidence

• Snapshot cleanup traverses modules but not the HAS_ARTIFACT subtree.
• Bolt full runs never remove absent artifact relationships.

Changes

• Reconcile the current application's artifact subtree on full runs.
• Preserve globally shared PURL package nodes.

Risks and boundaries

• Targeted runs retain their existing non-pruning behavior.
• Artifact text and schema contracts remain unchanged.

Verification

• bun test test/artifacts.test.ts
• RUN_CONTAINER_TESTS=1 bun test test/neo4j-bolt.test.ts
• bun test
• bun run typecheck

I checked the relevant issues, comments, pull requests, and discussions; this pull request is not a duplicate.

Disclosure

Investigated thoroughly with GPT-5.6 at extra-high reasoning effort.
I used Oh My Pi as the agent framework.
This report is not generic or unreviewed AI-generated output.
Its claims were checked against the cited evidence.
It includes the relevant detail intended to help maintainers resolve the issue.
If reports like this are not useful to the project, please let me know.
I will refrain from submitting similar reports.
My intent is to help without wasting maintainer time or energy or discouraging their work.
Thank you for your work.