fix(log): await cleanup and sort files before deletion

[djnawara]

Summary

• Await cleanup() in init() to prevent race condition where cleanup could run concurrently with file creation
• Sort files before slicing to ensure oldest files are deleted, not arbitrary files based on filesystem order

Problem

Log files were being deleted immediately after creation due to two issues:

1. cleanup() was called fire-and-forget (not awaited), creating a race condition
2. Bun.Glob.scan() returns files in arbitrary filesystem order, so slice(0, -10) was deleting random files instead of the oldest ones

Fix

• Added await before cleanup() call
• Added .sort() before .slice(0, -10) to ensure lexicographic order (which matches chronological order for the YYYY-MM-DDTHHMMSS.log filename format)

Tests

Added 8 tests covering:

• File creation (timestamp name, dev.log)
• Cleanup threshold behavior (5, 10, 11 files)
• Oldest file deletion
• Newest 10 files preserved
• dev.log excluded from cleanup (doesn't match glob)
• New log file created after cleanup runs