stash eql install can't install EQL v4 — add --eql-version 3|4|all #1143

Background

stash eql install installs EQL's SQL into a customer database. After #1142,
@cipherstash/eql carries two bundles: v3, for the TypeScript SDK's
cipherstash-client columns, and v4, for Stack Encrypt's (the Go SDK).

Problem

The CLI only knows v3. A Go project can't install v4, and a team moving from
TypeScript to Stack Encrypt needs both at once.

Proposal

1. Add --eql-version 3|4|all, defaulting to 3, which is today's behaviour.
   all is the documented way to migrate.
2. Make verify, status and the bundle-digest check aware of both bundles.
3. Add pty end-to-end tests.
4. Update skills/stash-cli, skills/stash-indexing and
   skills/stash-postgres in the same PR, and add a stash changeset.
5. The default changes to 4 later, announced in advance, once the
   TypeScript SDK has moved to Stack Encrypt.

Needs #1142. Decided in ADR-0002 (#1139).