The handler stores packages as {channel}/{name}, which purl writes as pkg:conda/conda-forge%2Fnumpy. Package rules name the channel as the namespace (pkg:conda/conda-forge/numpy) and get mapped to that form, with the package name lowercased the way conda treats it. A key without a channel or with an empty part could never match and is refused.
The mirror can't fetch conda packages today, so there's no mirror test.
Refs #306
