Jooris Hadeler
5bf4a494cb
Introduces fluxc/src/diagnostics.rs with Level (Critical, Error, Warning, Note), Label (Primary/Secondary with optional message), and Diagnostic types. Diagnostic::render(src, filename) produces rustc-style output: colored header, --> file:line:col pointer, source line with gutter, and ^ / - underlines aligned to the offending span. Replaces the flat ParseError struct in the parser; all five error sites now emit Diagnostic values with source-pointing labels.