chore: scrub personal gmail from docs/configs (estate-wide sweep)

Replaced jonathan.jewell@gmail.com with j.d.a.jewell@open.ac.uk per
the hyperpolymath author-attribution rule (the gmail is banned;
j.d.a.jewell@open.ac.uk is the canonical non-Git-context address).

PLACEHOLDERS files got a generic user-old@example.com so they remain
useful as templates.

.mailmap files in this repo (if any) are intentionally left — they
are the legitimate git mechanism for remapping historical commits
authored under the old gmail to the correct open.ac.uk address.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

v-ecosystem/v-graphql/PLACEHOLDERS.md

@@ -37,7 +37,7 @@ sed -i "s/2026-03-13/$(date +%Y-%m-%d)/g" $(grep -rl '2026-03-13' .)
 |---|---|---|---|
 | `Jonathan D.A. Jewell` | Full legal name | `Jane Doe` | SPDX headers (all files), MAINTAINERS.md, .mailmap, .reuse/dep5, docs/AI-CONVENTIONS.md |
 | `j.d.a.jewell@open.ac.uk` | Primary contact email | `jane@example.org` | SPDX headers (all files), .mailmap, .reuse/dep5, .well-known/humans.txt |
-| `jonathan.jewell@gmail.com` | Previous/secondary email (for .mailmap) | `old@example.com` | .mailmap |
+| `user-old@example.com` | Previous/secondary email (for .mailmap) | `old@example.com` | .mailmap |
 | `The Open University` | Author's organization/affiliation | `Acme University` | project-metadata.k9.ncl |
 | `Jewell` | Author surname (for citations) | `Doe` | docs/CITATIONS.adoc |
 | `Jonathan` | Author first name (for citations) | `Jane` | docs/CITATIONS.adoc |