V-L1-D1: add Related repos cross-link to verisimdb-data

[hyperpolymath]

Context

Two repos under the "VeriSimDB" brand describe different products:

• hyperpolymath/verisimiser — Rust CLI that augments any database with octad capabilities (drift, provenance, temporal, …)
• hyperpolymath/verisimdb-data — git-backed flat-file storage for "panic-attack scan results and drift detection data"

A reader landing on either repo from a search result has no way to know:

1. Whether the other repo is the same product or a different one
2. Whether they need both
3. Which is canonical

What to do

Add a short "Related repos" section to each README (after the title, before "What is this?"):

• In verisimiser/README.adoc:

  Related: verisimdb-data — the flat-file scan/drift store that verisimiser optionally writes to. Verisimiser does not require it.

• In verisimdb-data/README.adoc:

  Related: verisimiser — the augmentation CLI. This repo holds its drift snapshots and scan-ingest output. Standalone consumers (panic-attacker, hardware-crash-team) also write here.

If the actual relationship is different from what's sketched above (which it may well be — see V-L1-J1), adjust accordingly. The goal is: a reader can answer "do these two repos belong together?" from the first paragraph of either README.

Acceptance

• Both READMEs have a "Related repos" section with a one-line description and link
• The two descriptions are consistent (don't claim different relationships)