Modularize benchmark support and graph memory tests

[yvette-carlisle]

Summary

• split graph memory integration tests into entity, facts, helpers, and predicate modules
• split real-world benchmark fixtures for production ops, work continuity, consolidation knowledge, and report paths into focused modules
• keep existing public test/support APIs wired through normal Rust mod declarations and re-exports

Validation

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

Size

• 24 files changed, 1799 insertions(+), 1771 deletions(-)