Split real-world benchmark report contracts

[yvette-carlisle]

Summary

• Split job_reports.rs into a facade plus focused job report contract modules.
• Split summary_reports.rs into core, domain, and suite report contract modules.
• Split external_adapter_reports.rs into detail, manifest, misc, and summary report contract modules.

Validation

• cargo make fmt-rust-check
• cargo make check-rust
• cargo make test-rust (403 passed, 92 skipped)

Review Notes

• Batched as one PR to avoid repeated remote CI waits for adjacent low-risk report-contract splits.
• Batch-level skeptic passed with notes: effective facade surface is preserved; moved internal fields use pub(crate) inside private child modules and facades re-export the same contract names with pub(super).