Function needs_project_error 

pub fn needs_project_error(a: &AssetDecl) -> CompileError

bynk.asset.needs_project for a: a single-file build emits one module and no Worker, and has no project root to find assets/ under, so it cannot ship a file. Checking a single file (bynk check page.bynk) is unaffected; building one that declares an asset is refused. Build the project instead.