nixStats-multi

### Added
- Just run `/nixstats` to open the config — dropped the redundant `config` argument.

### Changed
- **Config screen redesign** — far more compact, fits more stats on one screen:
  - Rested / Warning / Critical colors collapsed to a single line (click a swatch to cycle presets, right-click to step back).
  - Scale, Text, Pad, Sync and the Warning/Critical thresholds are now up/down spinners instead of full-width sliders.
- **Stat values now match Minecraft's Statistics screen exactly** — counts as `1,234,567`, distances in km/m/cm, play-time as `d/h/m` — all via the game's own formatters. The phantom timer keeps its `mm:ss` countdown.

### Fixed
- **Damage stats were reading 10× too high** — now correct.
- Distance stats no longer show raw centimeters (`…K`) — proper km/m/cm now.
- `/nixstats` reliably opens the config on every version (a chat-close timing issue could swallow it on some 1.21.x builds).