StreamHandler.emit() writes formatted output to a Writable stream. ConsoleHandler maps log levels to console.warn/error/log. StderrHandler emits via console.error. handleError() logs diagnostics instead of throwing. FileHandler throws NotImplementedError on construction. Removed Node.js stream import and conditional require() block.
Add missing getter for formatter property. Fix format() to return the formatted string instead of discarding it. Fix level setter to assign to _level instead of recursing infinitely.