fix(ops): close the type-argument list that made the dead-letter read a comparison (#7095)

`findDeadMessages` opened two type-argument lists — `$queryRaw<` and
`Array<` — and closed only one before `(`. That is not a syntax error:
TypeScript falls back to parsing the whole expression as a `<`
comparison, so the emitted JavaScript is `$queryRaw < Array(sql)`. The
query never reached Postgres, `rows` was a boolean, and every load of
/ops/event-sourcing/dead-letters died on `rows.map is not a function`
in 3ms, surfacing as a spinner (react-query retrying) and then a
generic "unknown error" header.

`pnpm typecheck` could not catch it, because a comparison typechecks.
The existing coverage is integration-only, so the guard added here is a
unit test that calls both dead-letter reads against a stubbed Prisma
and asserts on what came back — it fails with the production
`TypeError` on the unfixed code and runs on every change.

Swept every other `$queryRaw`/`$executeRaw` site in the app by
comparing the emitted JavaScript; this was the only one affected. The
SQL itself was validated against a real Postgres schema — it had never
executed before.