Move `app/nodes/publish_findings/node_test.py` into `tests/nodes/publish_findings/`

[VaibhavUpreti]

Why This Matters

publish-findings coverage is currently split between inline and non-inline tests.

Read First

• app/nodes/publish_findings/node_test.py
• tests/nodes/publish_findings/

Scope

1. Move the file into tests/nodes/publish_findings/.
2. Merge duplicate assertions only if they truly overlap.
3. Delete the inline copy.

Tests / Coverage

• no new assertions are required
• first prove the moved tests still pass
• keep the current publish-flow assertions intact

Acceptance Criteria

• all publish-findings tests live in one test tree
• the inline file is removed
• duplicate coverage is reduced, not increased