fix(gitignore): ignore infra/*-tenant.personas.json (ADR-0026)

The per-persona Entra oid map consumed by prisma/seed.ts was missing
the matching ignore pattern when the personas seed work landed.
infra/test-tenant.personas.json has been showing up as untracked
(??) across multiple sessions, exposing it to an accidental
'git add .'. Mirror the existing *-tenant.entra.json pattern:
ignore the tenant-private file, keep the .example.json template
tracked.

Verified via 'git log --all -- infra/test-tenant.personas.json'
that no commit ever referenced this path, so no history rewrite
needed — pure forward-only fix.

.gitignore

@@ -35,6 +35,11 @@ pnpm-debug.log*
 infra/*-tenant.entra.json
 !infra/*-tenant.entra.example.json
 
+# Tenant-private Entra per-persona oids consumed by prisma/seed.ts
+# (ADR-0026 §"Seed personas"). Same pattern — commit only the example.
+infra/*-tenant.personas.json
+!infra/*-tenant.personas.example.json
+
 # OS / editor scrap
 .DS_Store
 Thumbs.db