YlPlatformConformanceFixture class abstract interface

An implementation-owned deterministic harness. source must be supported with default load options, committing initially in buffering without Ready or First Frame until the explicit hooks below inject them. Each created player is isolated. Hook futures complete after their input is processed and its observable state/events are published, including ignored/duplicate inputs. Private transport reply ordering and controller milestone futures belong in adapter/controller suites, not this SPI-only harness.

For metadata secrecy checks, use distinctive canary values of at least 16 characters in request headers/credentials, URI user info and queries. Short values such as 2 can occur innocently in diagnostics and are not substring secrecy markers. Even long values must be chosen to avoid ordinary output: these finite checks cannot establish information flow from coincident text.