When docker-prep packs @bytelyst/* as tarballs, a second physical copy of
@bytelyst/errors can be created, breaking prototype identity. The
fastify-core error handler's 'error instanceof ServiceError' then returned
false, mis-mapping ConflictError/BadRequestError/etc. to HTTP 500.
Fix: brand ServiceError instances with a global Symbol.for() key and add a
Symbol.hasInstance that recognizes any branded instance for the base class,
while preserving prototype-chain semantics for subclasses. Resilient to
duplicated module copies without touching call sites.
- errors: brand + custom hasInstance (+3 cross-instance unit tests)
- fastify-core: regression test (duplicated-copy ServiceError -> 409 not 500)
- bump @bytelyst/errors 0.1.11 -> 0.1.13, published to Gitea registry
