feat: let a producer say how its graph reads, without teaching the platform

[endrix]

Four hooks a dataflow producer needs and could not have. Each follows the pattern external-node-by-meta established: the producer states a fact, the platform derives something selectable from it, and the naming happens in the product's own stylesheet. No new product word enters core, and the gates stay green because there is nothing product-shaped to find.

The kind hook was already here and only half wired

<kind>-node was emitted inside the external branch, so it worked for exactly the case the first product needed and silently did nothing for any other. A producer introducing a kind of its own got a node the platform renders happily and its own stylesheet cannot select, with nothing anywhere to say why. Nothing about the hook ever depended on externality. It is hoisted, so every node gets it.

This sits alongside the node-families mechanism from #36 rather than competing with it: families are a product's declared vocabulary, this is a fallback selector derived from whatever kind arrived.

Port roles

control had a class from before roles were general, and the property panel and port views read it, so it stays. Every role now also gets port-role-<role>.

This matters more than styling. Roles are the axis a reader wants to switch off: wiring present on every single element carries no information until the moment it does, and without a hook there is nothing to hang that switch on.

Edges gain role, width and undirected

A dataflow network carries several kinds of connection at once — one that carries tokens, one that carries a value, one that carries the thing clocking all of it — and drawn identically they can only be told apart by tracing them by hand. undirected lets a producer ask for the no-arrow edge type that already existed for structural wiring, for a connection with genuinely no direction to draw.

Feedback, which has a real design question in it

The derived answer is a fact about the drawing: which edges point backwards in the order the layout will use. That is the honest answer when nobody knows better, and it stays the default.

But a producer often does know better, because in its own terms a loop has a designated closing element and the shape cannot show which one it is. Several edges of one cycle are equally good candidates by shape alone, and the greedy sequencing picks among them by degree. So meta.feedback anywhere in a document switches that whole graph to the producer's answer.

All-or-nothing, deliberately. The test that pins it names the forward edge of a two-node loop — a choice the derivation would never make, which is what proves the declaration is honoured rather than merely agreeing. Merging the two sets would mark one cycle twice, once where the producer said and once where the heuristic guessed, and a reader has no way to tell which mark carries meaning.

Compatibility

Everything except the hoisted kind class is inert unless a producer sets one of the new keys, so a document that declares nothing behaves exactly as before. The derived-class helper checks its input against a class-name pattern, because the value is interpolated into a class attribute and a producer is not necessarily careful; there is a test with a space and a quote in a kind.

Verification

• 12 new tests in producer-declared-render-hooks.test.ts
• Full platform suite passes, 4/4 neutrality gates pass, build succeeds

Still outstanding from the same list

Both client-side and larger: the hide-by-role toggle, and edge labels, which the edge view has no notion of today. The first consumer of this reached the same conclusion about roles from the other direction and filters them producer-side instead, which also removes the ports rather than leaving dangling pins.