html_to_markdown_ffi_platform

Shared envelope core for the html_to_markdown_ffi federated family: the transport seam (PlatformHtmlToMarkdownFfiEnvelope — payload decode, typed error mapping, timeout) and the native-library resolver seam (HtmNativeLibraries) adapters use to contribute their bundled binaries to the preserved loading chain.

Adapters depend on this package plus the app-facing html_to_markdown_ffi.