Error on mis-grouped newdata in cumulative add_* functions

DESCRIPTION

@@ -1,7 +1,7 @@
 Package: pammtools
 Title: Piece-Wise Exponential Additive Mixed Modeling Tools for Survival Analysis
-Version: 0.8.0
-Date: 2026-06-17
+Version: 0.8.1
+Date: 2026-07-08
 Authors@R: c(
     person("Andreas", "Bender", , "andreas.bender@stat.uni-muenchen.de", role = c("aut", "cre"), comment=c(ORCID = "0000-0001-5628-8611")),
     person("Fabian", "Scheipl", , "fabian.scheipl@stat.uni-muenchen.de", role = c("aut"), comment = c(ORCID = "0000-0001-8172-3603")),

NEWS.md

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+# pammtools 0.8.1
+
+## Enhancements
+* The cumulative post-processing functions (`add_cumu_hazard()`,
+  `add_surv_prob()`, `add_cif()` -- for both their default and `pamm_ic`
+  methods -- and `add_trans_prob()`) now **error** when `newdata` is not grouped
+  so that the time variable is unique within each group (typically a forgotten
+  `group_by()`), instead of silently accumulating cumulative quantities across
+  distinct covariate profiles / causes / transitions and returning wrong
+  curves. This generalises the guard already used for the interval-censoring
+  pooling path (and mirrors the `stopifnot()` guard in the RMST example). All
+  of these functions accept `check_grouping = FALSE` to opt out (e.g. for
+  advanced workflows that intentionally accumulate over rows with varying
+  covariates). The guard detects mis-grouping via repeated time values within
+  a group: grids built with `make_newdata()` are always caught, but hand-built
+  grids stacking profiles with *disjoint* time grids are indistinguishable
+  from a single profile with time-varying covariates and pass undetected.
+
 # pammtools 0.8.0
 
 This release collects all changes since the last CRAN version (0.7.4),