gofmt: bring internal/ and cmd/ back to gofmt -l clean

Mechanical `gofmt -w ./internal ./cmd`. Mostly struct-field realignment that
had drifted, plus a few trailing-newline fixes. No behaviour change — gofmt is
semantics-preserving, and build/vet/test are green either side.

Split out from the code-review fixes that follow so those stay reviewable
instead of hiding inside a wall of realignment.

internal/plugin/uno.go

@@ -2039,5 +2039,3 @@ func (p *UnoPlugin) recordGame(game *unoGame, result string, potBefore float64)
 		time.Now().UTC().Format("2006-01-02 15:04:05"),
 	)
 }
-
-