Increase timestamp precision to milliseconds in serial console log

[SJ7F]

Summary

Motivation & Context

Closes #30

Changes

• Changes timestamp format in serial console logs from HH:MM:SS to HH:MM:SS.SSS

Screenshots / Demos (if UI)

How to Test

1. Connect a data source
2. Switch to the Console tab and verify that timestamps have millisecond precision
3. Check that timestamps are still localized properly

Checklist

• I ran npm run lint and fixed any issues
• I ran npm run typecheck (TypeScript) with no errors
• I ran npm test and tests pass
• I ran npm run test:coverage if code paths changed significantly
• I added/updated tests where appropriate
• I updated docs/README if needed
• No breaking changes without clear migration notes

Additional Notes

This uses HH:MM:SS.SSS instead of HH:MM:SS:XXX which was suggested in #30