Implement StreamHandler.emit(), ConsoleHandler for browser console
API, and a browser-compatible stream abstraction. Design handler
base with issue 13 (localStorage handler) in mind.
Implemented %-style field substitution in PercentFormatterStyle,
JS Date-based formatTime with strftime token support and ISO8601
fallback, Error.stack-based formatError, and LogRecord.getMessage.
Added message, name, msg, args fields to LogRecord.
Implement PercentFormatterStyle._format() with %-style field
substitution, Formatter.formatTime() using JS Date/Intl, and
Formatter.formatError() using Error.stack. Add datetime helpers.
Added info(), warning(), error(), and critical() methods to Logger,
each gated by isEnabledFor(). All level methods tested including
effective level filtering.
Fixed logic bugs across manager, config, logger, handler, and
formatter modules. Manager.getLogger() now correctly creates and
returns loggers with hierarchy setup. Config.basicConfig() reads
the correct option fields and has proper control flow. Logger
isEnabledFor() caches correctly, _log() calls handle(), makeRecord()
uses Object.keys(). Handler has working formatter getter, format()
returns a string, and level setter no longer recurses. Formatter
has a format() method. Added unit tests for all four modules.
