Closed Beta v3 zip shipped with the dev/ directory included

**Status: needs triage** (build process)

## Observation
The MultiplayerClosedBeta-v3.zip distribution of the API mod contains `dev/init.lua` (and its contents differ from the repo's version). The repo's release CI (`.github/workflows/strip-dev.yml`) strips `dev/` from release builds, so the beta zip appears to have been built from a working tree through a path that bypasses that step.

## Impact
Low today — `dev/init.lua` only enables env-var-driven dev auth, and the dev impersonation endpoint 404s against production servers. But it means beta testers are silently running dev-mode clients, and anything added to `dev/` in the future would ship to them unnoticed. Beta builds should go through the same strip step as releases (or include dev tooling deliberately as a documented decision).

Commencez par .github/workflows/strip-dev.yml et retracez la manière dont MultiplayerClosedBeta-v3.zip a été produit, en recherchant le point d’entrée de l’empaquetage de la bêta qui a contourné l’étape strip. Vérifiez le contenu de l’archive obtenue ; le travail est considéré comme terminé lorsque les builds bêta excluent systématiquement dev/ ou que le dépôt documente une décision délibérée de l’inclure.

Rédigé par le modèle d'indexation à partir du texte de l'issue.