Wire count ergonomics. Infer wire count from context

[mofosyne]

For something like below

cables:
  B1: {}

connections:
  - X1: [1,2,3,4]
  - B1
  - X2: [1,2,3,4]

It should be inferred that we want 4 wires and that B1 wire set is [1,2,3,4]

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If we go more ambitous... perhaps

Example:

paths:
  - X1 -> B1 -> X2

This compiles into:

- X1: [1,2,3,4]
- B1
- X2: [1,2,3,4]

Which will decompose to:

- X1: [1,2,3,4]
- B1: [1,2,3,4]
- X2: [1,2,3,4]

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Anyway be interesting to hear other's people's perspective on overall wireviz syntax ergonomics