fix(sdk): createPedestrian emitted a shape type no consumer recognises

[kosuke55]

Problem

Scenes built with createPedestrian silently lose every pedestrian:

const snapshot = createSnapshot([...lane, createVehicle(100, 25), createPedestrian(300, 25)])
exportToOpenScenario(snapshot, {})
// → 1 ScenarioObject (the vehicle). The pedestrian is gone, with no warning.

Cause

createPedestrian returned type: 'pedestrian', but nothing in the SDK or the editor handles that shape type:

• the editor has only ever stored placed participants as vehicle — pedestrians are a templateId, not a shape type
• exporter/openscenario.ts skips anything that is not vehicle, then picks <Pedestrian> vs <Vehicle> from PEDESTRIAN_PATTERNS

So the factory disagreed with its own consumers. createVehicle and createPedestrian differ only in the default templateId ('filled'), which already matches the exporter's pedestrian patterns — the shape type was the only thing wrong.

Fix

Return type: 'vehicle', and document why in a doc comment: the name createPedestrian naturally invites type: 'pedestrian', so without an explanation the same change is likely to be reintroduced.

Verification

With plain Node against the built dist/:

pedestrian shape type: vehicle / templateId: filled
entities: 2 [ 'Vehicle_0', 'Pedestrian_1' ]
has <Pedestrian>: true
pedestrianCategory: pedestrian

Existing suite: 325 passed, 4 skipped.

Test

Added __tests__/helpersFactoryContract.test.ts.

It runs factory output through the exporter instead of asserting the shape type. Asserting shape.type === 'vehicle' would pass while telling us nothing about whether a pedestrian actually survives export — and the consequence is the part that was broken.

No existing test referenced createPedestrian at all, which is why this went unnoticed. I confirmed both new cases fail when the old type is restored.