feat(logger): Create @lytics/kero zero-dependency logger

[prosdev]

Summary

Creates @lytics/kero, a zero-dependency TypeScript logger inspired by Pino.

Features

• Core logging: trace, debug, info, warn, error, fatal levels
• Pino-inspired API: Structured logging with object + message pattern
• Child loggers: Context inheritance for request tracking
• Formatters:
  • Pretty (colored, human-readable)
  • JSON (machine-readable, Pino-compatible)
• Console transport: stdout/stderr routing by level
• Presets: development, production, test configurations
• Timer utility: startTimer() for measuring durations
• Success method: success() for success messages with ✔ icon
• Configurable icons: Unicode (» ○ ● ✔ ▲ ✖ ✘) or emoji

Usage

import { kero, createLogger } from '@lytics/kero';

// Default logger
kero.info('Server started');
kero.success('Deployment complete');
kero.error(new Error('Failed'), 'Request failed');

// Custom logger with icons
const logger = createLogger({
  preset: 'development',
  formatter: new PrettyFormatter({ icons: true }),
});

// Child loggers
const reqLogger = logger.child({ requestId: 'abc-123' });
reqLogger.info('Processing');

// Timing
const done = logger.startTimer('db-query');
await db.query(sql);
done(); // logs: "db-query completed (42ms)"

Test Coverage

• 62 tests passing
• 100% line coverage
• 100% function coverage
• 94% branch coverage

Why Zero Dependencies?

1. Maximum portability across projects
2. No version conflicts
3. AI-assisted development makes building from scratch fast
4. Full control over behavior and debugging

Closes #46