fix: keep a literal % in logpoint messages that interpolate nothing - #2445

A logpoint message with a literal % and no {expression} shows every % doubled in the Debug Console. 50% done logs 50%% done, while {1} 50% done logs 1 50% done. The compiler escapes % because the message becomes a console.log format string, but format specifiers are only applied when there is more than one argument, so with nothing interpolated the escape is never undone.

This uses the escaped format string only when at least one expression was interpolated, and passes the message through unchanged otherwise.

• Ran: npm run test:unit -- --grep logMessageToExpression. The two new cases fail on main (console.log("50%% done, 100%%")) and pass with the change. The existing escaping case still covers the interpolated path.
• Ran: npm run test:unit, no new failures (the 8 NodeBinaryProvider failures also happen on main).
• Checked: npm run test:types, dprint check and eslint --max-warnings=0 on the touched files are clean.