behavioral-guarantee-claims.md: 13 rows link source files retired with Relay V1

`release/notes/behavioral-guarantee-claims.md` links each claim to the source file it was quoted from. Thirteen of those repository-relative links point at files that Relay V1's retirement removed, so they resolve to nothing on `main`.

## The rows

| Target | Rows | Line(s) |
| --- | --- | --- |
| `docs/site/src/content/docs/explanation/consultation-flow.mdx` | 7 | 25-31 |
| `crates/registry-relay/docs/api.md` | 2 | 67, 68 |
| `crates/registry-relay/docs/configuration.md` | 1 | 69 |
| `crates/registry-relay/docs/ops.md` | 1 | 66 |
| `crates/registry-relay/docs/xlsx-readiness-contract.md` | 1 | 70 |
| `docs/site/src/content/docs/tutorials/deploy-standalone-with-own-data.mdx` | 1 | 71 |

All six were last shipped at `v0.19.0`.

## Suggested fix

The file already has a convention for this. The retired Notary rows link their pages at `v0.16.3`, the last release that shipped them, and the preamble says why. The retired `start/when-to-use` chooser row was pinned the same way at `v0.27.0` in #916.

Applying it here means rewriting each of the thirteen links to `https://github.com/registrystack/registry-stack/blob/v0.19.0/` and adding one preamble sentence covering the Relay V1 retirement.

Worth deciding alongside: whether these rows should be pinned at all, or dropped. The Notary preamble says its rows are kept as the historical record and are "not verification work for a maintained product." Relay V1's rows are in the same position, since Relay V2 is a different runtime with its own contracts under `products/relay-v2`. Pinning preserves the record; dropping shrinks an inventory whose remaining verification value is only in the rows for maintained products.

## Notes

- Found while retargeting the `start/when-to-use` row in #916. These six predate that branch and were left alone as out of scope.
- Nothing currently validates repository-relative links under `release/notes/`, which is why thirteen of them could go stale unnoticed across two product retirements. A check there would catch the next one, but it is a separate call from fixing these rows.

Open release/notes/behavioral-guarantee-claims.md and compare the thirteen Relay V1 rows with the retired Notary convention and the preamble. Decide whether to preserve the historical rows or remove them; done means the chosen treatment is applied consistently and the preamble explains it, with all affected links no longer broken.

Written by the indexing model from the issue text.