fix: improve quota sidebar readability

[slkiser]

Summary

• add one blank line between grouped quota entry blocks and sidebar detail rows
• render readable sidebar text at the normal text color while keeping progress bars and separators muted
• cover grouped formatting, line colors, and sidebar spacing with focused tests

Linked Issue

No linked issue. This is limited to quota sidebar and grouped-output readability.

OpenCode Validation

• Current production released OpenCode version tested: Not applicable
• Why this version is relevant to the fix: The changed formatting and TUI rendering paths are covered by unit and smoke tests.

Quality Checklist

• I ran pnpm run typecheck
• I ran pnpm run build
• I ran pnpm test
• This change is focused and avoids unrelated behavior changes
• I updated or added tests when behavior changed
• Docs do not need changes because commands and configuration are unchanged
• Provider changes do not apply