Every merge rule, AST gate and provenance decision was derived from reading
upstream source and proven only against fake backends, so nothing had ever run
against a real PuppetDB.
- Add an e2e suite behind the `e2e` build tag and a `make e2e` target
- Stand up two openvoxdb backends on their own PostgreSQL with testcontainers
- Load facts, reports and catalogs over the command API, waiting on processing
- Assert the union, freshness dedupe, summed aggregates, provenance gating,
X-Backends, backend death and recovery, and the report paths
- Drive Puppetboard and node-lookup against pdbmux as real clients
- Record three known gaps as skips that fail once the gap closes