Function is_declaration_file_path 

pub fn is_declaration_file_path(path: &Path) -> bool

True when the path’s final component looks like a TypeScript declaration file (.d.ts, .d.mts, .d.cts). Used to seed declaration files as overall entry points so ambient typeof import() references stay alive; see ModuleGraph::build_with_declaration_seeding for the exception.

The analysis layer reuses this predicate. Keep it in sync with the discovery walk’s declaration-file predicate, which exempts declaration files from the file-size skip.