chore(tests/lean/run/group3): cleanup test
feat(frontends/lean/notation_cmd): notation defined in context overrides existing ones
refactor(frontends/lean/parser_config): merge notation_ext and mpz_notation_ext
feat(frontends/lean/notation_cmd): allow local numeric notation
chore(frontends/lean/elaborator): fix field name
refactor(frontends/lean/elaborator): expose elaborator class
fix(frontends/lean/elaborator): style
feat(bin/linja): enforce path separator '\' on Windows platform