Implement pluggable renderers and exporters for common output formats #256

Goal

Render the same structured 2.x projections into multiple human- and machine-readable formats through pluggable adapters.

Scope

• Provide console/table rendering.
• Provide Markdown rendering.
• Provide JSON, YAML, and XML serialization adapters.
• Provide XLSX export for tabular/reporting workflows.
• Keep format-specific styling and dependencies outside domain and connector layers.
• Make additional renderers/exporters discoverable through a small extension contract.

Acceptance criteria

• One projection can be emitted in multiple formats without recalculation.
• Console, Markdown, JSON, YAML, XML, and XLSX outputs use shared structured input.
• Format adapters do not contain broker-specific business logic.
• Export behavior has deterministic regression coverage.