feat: add Ladybug graph database exporter

[eduardpaul]

feat: add Ladybug graph database exporter

🚀 Summary

This PR introduces a new exporter for Ladybug, allowing users to export their knowledge graphs into a format optimized for Ladybug's embedded engine and its web-based visualization tool, Ladybug Explorer.

✨ Key Changes

• New Exporter Implementation: Added `LadybugExporter` which generates a single `.cypher` file containing:
  • DDL: `CREATE NODE TABLE` and `CREATE REL TABLE` statements defining the graph schema.
  • DML: Structured `CREATE` and `MATCH/CREATE` statements for nodes and relationships.
• Native Schema Mapping:
  • Maps graph nodes to a unified `GraphNode` table and edges to `GraphEdge`.
  • Leverages Ladybug's native `MAP(STRING, STRING)` type for metadata, ensuring better queryability compared to plain JSON strings.
• CLI Integration: Updated `Graphify.Cli` to support the `--format ladybug` flag.
• Documentation: Added a detailed `docs/format-ladybug.md` covering installation, import, and visualization using Docker.
• Test Coverage: Added extensive unit and integration tests to verify Cypher generation and referential integrity.

🛠 Usage

# Generate the Ladybug Cypher script
graphify run ./src --format ladybug

# Import into a Ladybug database
lbug graph.db < graphify-out/graph.ladybug.cypher

✅ Verification Results

• Unit Tests: `LadybugExporterTests.cs` covering schema generation and property mapping.
• Integration Tests: Verified end-to-end pipeline execution with Ladybug output.
• Architecture: Updated `ARCHITECTURE.md` to reflect the new exporter in the project structure.

[elbruno]

Thanks @eduardpaul , this is nice!
Let me take a look and I'll merge it

[elbruno]

Applied the requested follow-up fixes and validated them locally.

What changed:

• Fixed Ladybug metadata query docs to use size(map_extract(...)) > 0.
• Added tests for null relationship fallback to RELATED_TO.
• Added tests for edge metadata emission.
• Added multi-edge and whitespace output-path coverage.
• Fixed the orphan-edge test to remove the dead split on a non-existent marker.
• Added a dedicated Ladybug integration output-shape test.
• Added PipelineRunner routing coverage for ladybug.

Validation:

• dotnet test graphify-dotnet.slnx --no-build --verbosity minimal passed locally.
• Tank reviewer gate: APPROVED.