Rebuild spec: point to the edge-bench-rs README

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

REBUILD.md

@@ -111,6 +111,8 @@ dropping garbage; 28 TB of compressed overview traffic. Throughput goal:
    instead of ~6–7; the speed is still set by the NNTP connections. The
    cost: a second implementation of lib/headers, lib/release, lib/rules and
    the chunk format, kept identical (check.ts) for as long as both exist.
+   Findings, how to run both and how to compare their outputs:
+   `tools/edge-bench-rs/README.md`.
    Per lease: compressed chunks of 10–50 k lines, in order →
    parse subjects → skip crossposts outside their owner group (of the
    indexed groups in the article's Xref, the one with the lowest priority