fix(tui): right-align the header timer without a separator

[aiev]

Summary

• Keep the title and progress on the left and pin the standalone timer to the right edge of the header.
• Remove the separator before both the live timer and the finished done in … label.
• Preserve the header divider, collapse behavior, and per-task timing.
• Add timer-label regression tests, update the README, and prepare patch release 0.4.1.

Validation

• npm run typecheck
• npm run build
• npm test — 43 tests passed
• npm pack --dry-run --json
• git diff --check