v0.2.1

Add unit tests and input validation for key algorithmic functions

• Add tests for compensate_data(), DE_pseudobulk(), run_FlowSOM(),
  run_modified_ransac(), and detect_aggregates(), which previously
  had no coverage.
• Add input validation with informative error messages to the same
  functions (class checks, missing/invalid args, mismatched columns).
• Fix a 1:nrow() indexing bug in detect_aggregates() that misbehaved
  on a zero-row aggregate_channels data frame.