v0.26.4

• New IConfigRegistry.PublishIfChangedAsync(configType, version, bytes, failOnDrift) extension — diagnostic publish that compares against existing bytes and returns PublishedNew / Unchanged / OverwrittenAfterDrift. failOnDrift: true throws ConfigContentDriftException (typed) — use in CI/prod to enforce "content changes require a version bump". Raw PublishAsync still silently overwrites; this helper makes drift visible.
• FileConfigCache<TConfig> filename now includes Patch: {Name}.v{Major}.{Minor}.{Patch}.bin (was v{Major}.{Minor}.bin). Pre-0.26.4 cache collapsed every patch of the same Major.Minor into one file — broken for hotfix patches and for content-derived dev-version workflows. Old-format files auto-evicted by the existing v*.bin cleanup glob on next Put.