ArtefactKino requires node label

[matt-beanland]

Node labels are optional

When node labels: is nil or [], ArtefactKino 0.1.4 does

** (ArgumentError) argument error
    (erts 16.1.1) :erlang.++("Engine", [])
    (artefact_kino 0.1.4) lib/artefact_kino.ex:51: anonymous fn/2 in ArtefactKino.vis_nodes/1
    (elixir 1.19.3) lib/enum.ex:1688: Enum."-map/2-lists^map/1-1-"/2
    (elixir 1.19.3) lib/enum.ex:1688: Enum."-map/2-lists^map/1-1-"/2
    (artefact_kino 0.1.4) lib/artefact_kino.ex:34: ArtefactKino.build_data/2
    (artefact_kino 0.1.4) lib/artefact_kino.ex:29: ArtefactKino.new/2
    #cell:dd5ocfjfzuw6mogx:24: (file)

[matt-beanland]

ArtefactKino will call Artefact.validate! immediately, however it is valid for a node to not have a label.

[matt-beanland]

#28 — ArtefactKino requires node label (closed in 0.1.5)

Root cause was upstream: artefact let through nodes with non-list
:labels (which then tripped the :erlang.++ in vis_nodes/1).

Fixed both sides. In artefact the validation rule-set rejects
non-list labels at op input. In ArtefactKino the kino calls
Artefact.validate!/1 on its input first thing, so a hand-built
struct with malformed fields raises Artefact.Error.Invalid (was
ArgumentError in 0.1.5) with structured reasons instead of a
cryptic render-time error.

artefact_kino 0.1.5 shipped this. artefact_kino 0.2.0 updated
the raise type to Artefact.Error.Invalid to match the new error
shape.

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