fabricatorPreset picks the first JLC stackup when several constructions match (4-layer 1.0 mm: 1080/2116/3313/7628) #4890

Problem

Since #4826, fabricatorPreset="jlcpcb_standard" resolves the board's pcb_stackup from its layer count, thickness and material only. JLCPCB offers several constructions for the same combination. For a 4-layer 1.0 mm FR4 board those are JLC04101H-1080, -2116, -3313 and -7628. Core takes the first match, and nothing lets the board say which one it is ordered with.

Repro

<board layers={4} thickness={1} material="fr4" fabricatorPreset="jlcpcb_standard" width="100mm" height="100mm" />

The emitted pcb_stackup is the 7628 construction: 0.2104 mm "7628 RC49%" prepreg, εr 4.4. Our board is ordered as JLC04101H-3313, which has 0.0994 mm prepreg, εr ≈ 4.1. Anything that reads pcb_stackup for impedance or loads gets the wrong answer: a 0.15 mm top trace comes out around 76 Ω instead of 50 Ω.

Proposal

Either of these would work, without guessing:

1. Let the board name its construction, e.g. jlcpcbStackup="JLC04101H-3313" beside fabricatorPreset. An explicit stackup prop like the one in Preserve physical stackup through board rendering and import #4410 would also cover it.
2. When more than one construction matches and none is named, emit no pcb_stackup, or emit a warning that says which constructions match.

Happy to test a fix.