extractGoVarConst used ChildByFieldName("name"), which returns only the first name field, so 'var a, b = 1, 2' and 'const ( C, D = 3, 4 )' surfaced only a/C. Iterate every "name"-field child so each declared identifier becomes its own symbol. Adds TestExtractGoVarConstMultiName.
FindSymbolRange returned the first AST node matching a name, so file_read with symbol_name silently read the wrong symbol when a name collided (e.g. two String() methods on different receivers, or a func and type sharing a name). New FindSymbolCandidates returns all matches; the file_read handler now errors on ambiguity, listing each candidate's node type and line range so the caller can disambiguate via symbol_kind or line_start/line_end. FindSymbolRange is kept (first match) for callers that don't need ambiguity detection. Adds TestFindSymbolCandidates.
lukaszraczylo