#839 displayed empty artifact-local keys and source-map original names as
`""` inside node identities, so `fetch("")` and `fetch('""')` (or
`sources: ["", "\"\""]`) produced the same node ID and merged two
distinct facts. Function nodes likewise exposed only a display label, so
`['']()` and `['""']()` were indistinguishable.
Admit the exact empty string in `artifact-local-key.key` and
`source-map-original.original_source`, keep the `""` substitution for
labels only, and record each function node's exact `name` in its
properties. Regenerate the catalog digests for the relaxed output schema.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>