fix: Address cascade delete bug, add missing test coverage, remove unused code

[Copilot]

Addresses feedback from PR #47 review: cascade delete could skip the universe node when dependencies are empty, missing test coverage for edge cases, and unused code in schemas.

Changes

• Fixed cascade delete bug: Modified Cypher query to always include universe in deletion list. Previously, UNWIND on empty dependents produced no rows, skipping the universe itself.

-- Before: UNWIND could produce zero rows
WITH u, sources + axioms + ... AS dependents
UNWIND dependents AS dependent  -- Empty list → no rows → u not deleted

-- After: Universe always included
WITH u, [x IN sources + axioms + ... WHERE x:Expected] + [u] AS nodes
UNWIND nodes AS n  -- Always includes u

• Added missing test coverage:

  • test_delete_universe_with_force_no_dependencies - Verifies force delete with empty dependents (count=1)
  • test_neo4j_client_execute_read_without_connection - Validates RuntimeError when not connected
  • test_neo4j_client_execute_write_without_connection - Validates RuntimeError when not connected

• Removed unused code:

  • authority field from MultiverseCreate (not stored or returned)
  • field_validator import from base.py (no validators use it)

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[Copilot]

Pull request overview

This PR addresses technical debt from PR #47 by fixing a cascade delete bug, adding missing test coverage for edge cases, and removing unused code from schema definitions.

• Fixed cascade delete bug where UNWIND on an empty dependents list would skip universe deletion
• Added test coverage for Neo4j client connection errors and force delete with no dependencies
• Removed unused authority field from MultiverseCreate and unused field_validator import

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
packages/data-layer/src/monitor_data/tools/neo4j_tools.py	Refactored Cypher query to use list comprehension with filtering, ensuring universe node is always included in deletion list by appending [u] after filtering
packages/data-layer/tests/test_tools/test_universe_tools.py	Added test to verify force delete correctly handles empty dependencies edge case (deleted_count=1)
packages/data-layer/tests/test_db/test_neo4j.py	Added tests to verify RuntimeError is raised when execute_read/execute_write are called without connection
packages/data-layer/src/monitor_data/schemas/universe.py	Removed unused authority field from MultiverseCreate schema (not stored in database)
packages/data-layer/src/monitor_data/schemas/base.py	Removed unused field_validator import from pydantic

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