fix(cli): refuse a --split-date or --axis that names nothing it built (improvise-tpm8)

context/test-evidence/formula-and-io.md

@@ -1919,3 +1919,27 @@ improvise-d0n6. The same with a raw `2024`, a generated group. Removing the
 `spelling_clash` call fails it the same way. The control,
 `a_raw_date_spelled_like_nothing_generated_is_kept_ungrouped`, passes either
 way, so a blanket refusal of every unparsed value fails it.
+
+### the_date_step_will_not_advance_over_a_spelling_clash
+
+improvise-d0n6 (Copilot on PR #322, and the adversarial review's B1). The
+spelling-clash refusal sat only in the build, so a wizard with a raw `2024` in
+a `%Y-%m-%d` column passed ConfigureDates and failed on NameModel, three steps
+from the `s` that fixes it. Before the check joined `validation_error` the
+test failed with the step already `DefineFormulas`; removing that call again
+reproduces it. It also toggles to the split shape and requires the step to
+advance, so a check that blocks forever fails.
+
+### split_date_naming_an_unknown_or_non_date_field_is_refused
+
+improvise-tpm8 class. `--split-date Nope` and `--split-date Revenue` (a
+measure) exited 0 and did nothing. Both now exit 1 naming the flag and the
+field; removing the check in `run_headless_import` fails both rows.
+
+### an_axis_naming_a_category_the_import_did_not_build_is_refused
+
+improvise-8jk6.3 review. `--extract Date:Month --axis Date_Month:column` used
+to build one `Date` category and drop the `--axis` for the vanished
+`Date_Month`, exit 0. It now exits 1 naming the category and `--split-date`.
+This also refuses any `--axis` naming an absent category, which was silently
+ignored before this PR as well.