support `lavaan.mi` models

library(lavaan.mi)

data("mtcars")

set.seed(20260205)
mtcars_amp <- mice::ampute(mtcars)$amp
imp <- mice::mice(mtcars_amp)


mod <- "
mpg ~ hp + vs
hp ~ am
"

fit.mi <- sem.mi(mod, data = imp)


performance::model_performance(fit.mi)
#> Warning: Objects of class `lavaan.mi` are not supported model objects.
#> NULL

This does work though:

lavaan::fitMeasures(fit.mi)
#> 
#> Test statistic(s) pooled using the D4 pooling method.
#>   Pooled statistic: "standard"
#> 
#>                  npar                  fmin                 chisq 
#>                 5.000                 0.671                43.900 
#>                    df                pvalue        baseline.chisq 
#>                 2.000                 0.000                77.570 
#>           baseline.df       baseline.pvalue                   cfi 
#>                 5.000                 0.000                 0.423 
#>                   tli                  nnfi                   rfi 
#>                -0.443                -0.443                 1.000 
#>                   nfi                  pnfi                   ifi 
#>                 0.434                 0.174                 0.446 
#>                   rni                  logl     unrestricted.logl 
#>                 0.423              -264.179              -241.989 
#>                   aic                   bic                ntotal 
#>               538.357               545.686                32.000 
#>                  bic2                 rmsea        rmsea.ci.lower 
#>               530.099                 0.809                 0.612 
#>        rmsea.ci.upper        rmsea.ci.level          rmsea.pvalue 
#>                 1.025                 0.900                 0.000 
#>        rmsea.close.h0 rmsea.notclose.pvalue     rmsea.notclose.h0 
#>                 0.050                 1.000                 0.080 
#>                   rmr            rmr_nomean                  srmr 
#>                20.736                20.736                 0.297 
#>          srmr_bentler   srmr_bentler_nomean                  crmr 
#>                 0.297                 0.297                 0.367 
#>           crmr_nomean            srmr_mplus     srmr_mplus_nomean 
#>                 0.367                 0.289                 0.289 
#>                 cn_05                 cn_01                   gfi 
#>                 5.367                 7.714                 0.508 
#>                  agfi                  pgfi                   mfi 
#>                -1.461                 0.102                 0.520 
#>                  ecvi 
#>                 1.684

Reproduce the example with lavaan.mi and trace performance::model_performance(fit.mi), comparing its behavior with lavaan::fitMeasures(fit.mi). Done means model_performance supports lavaan.mi objects without the current warning and returns performance metrics.