Compiler quick fixes: attach edits at report time, apply in rounds

For LSP quick fixes and a --fix CLI, have each compiler stage attach structured edits (span + replacement text) to the diagnostic when it reports it, instead of parsing fix hints back out of message text; the reporter already has the exact spans. Mark a fix isPreferred only when it's the diagnostic's sole fix, so editor auto-fix never has to choose. For the CLI, apply fixes in rounds: re-check after each pass, since one fix (like a missing space that broke parsing) can uncover others, and skip any fix whose edits touch an edit already chosen in the same round. Apply edits last-first so earlier offsets stay valid, and when deleting a statement that's alone on its line, remove the whole line including the newline. A diagnostic that needs operand spans not parsed yet (like a 'needs parentheses' error before the right operand exists) should be reported after that operand is parsed.