Split real-world benchmark report tests into modules

[yvette-carlisle]

Summary

• Split real-world benchmark dreaming report tests into dedicated sibling modules.
• Split external adapter benchmark assertions into focused modules for graph RAG, summaries, manifest summaries, and validation.
• Kept Rust module boundaries as normal mod files without include! or new #[path] indirection.

Validation

• RUSTC=/run/current-system/sw/bin/rustc cargo make fmt-rust && RUSTC=/run/current-system/sw/bin/rustc cargo make check