fix(ui): label usage by mode and separate sync status

[gcko]

Checklist

• Tests added/updated where needed
• DCO signed (use git commit -s)

Type

• Breaking change
• Bugfix
• Feature/UX improvement
• Chore

Description

• Update usage label to show Char(s) or Word(s) when switching count modes, and restore / 8192 Bytes in bytes mode.
• Add a ・ separator between usage and sync status for clearer visual grouping.

Issues

• None.

Notes

• If applicable, run pnpm lint, pnpm type:check, pnpm test.

Release notes

• Usage counter now displays the active unit label and UI includes a subtle separator between usage and sync status.