Dirty data and safe infeasibility handling

WFC stops early when design roles, source evidence, checksums, categories, or sample support are inconsistent. A stop is evidence to repair or review the inputs, not permission to choose a more convenient target.

Common safe responses are:

• remove outcome or undeclared columns before wf_prepare_design();
• correct a target file and update its evidence checksum;
• reconcile category spelling against wf_dims();
• document a deterministic support-based merge with wf_plan_cells(); or
• conclude that the requested calibration is not feasible.

design <- wf_prepare_design(
  design_only,
  id = "person_id",
  calibration = c("age_group", "region"),
  base_weight = "base_weight"
)

target <- wf_import_target(
  "population-margins.csv",
  "population-margins.csv.source.dcf",
  dims,
  key_map = c(age_group = "age_group", region = "region"),
  count = "population_count"
)

precheck <- wf_precheck(design$data, target, id = design$roles$id)
cell_plan <- wf_plan_cells(design, target, dims)

WFC never widens bounds, changes method, changes target, or approves a plan in response to infeasibility. Those are separate human decisions and may require a new workflow.