fix: close five final-review gaps in all-categories mode

- .detect_direct_suppressed() keys on (year, canonical_govid, category);
  all-categories mode collapses category to one literal value, so the key
  collides and the detector silently reports FALSE instead of "unknown".
  Report NA there instead, and stop isTRUE() in .build_provenance() from
  collapsing that NA back to FALSE. Schema widened to allow null.
- Refuse complete = TRUE + category = "All Categories": the completion grid
  has no per-category cells left to fill once categories are collapsed,
  so the prior silent 0-rows-filled result was never actually checked.
- cog_balances(category = "All Categories") returned zero rows with no
  error. .validate_verb_inputs() gains allow_all_categories (default
  FALSE); .verb_spendrev() passes TRUE, cog_balances() does not, so the
  three verbs share one place to reject it instead of drifting again.
- Fix the false `subtype = "operations"` argument claim (no such argument
  exists) in NEWS.md and an internal spending.R comment.

Adds three covering tests to test-all-categories.R for the three
behaviour changes above.

man/cog_spending.Rd

@@ -106,7 +106,12 @@ possibly-misleading `"harmonized"`/`"raw"` value.}
   component (when one exists), and
   `provenance$expenditure_concept_direct_suppressed` is `TRUE` -- the
   figure in those rows is the intergovernmental leg alone, not Direct +
-  IG.}
+  IG. When `category = "All Categories"` is combined with
+  `expenditure_concept = "total"`, this detection cannot run (it keys on
+  per-category rows, which all-categories mode collapses to one literal
+  value), so `expenditure_concept_direct_suppressed` is `NA` rather than a
+  possibly-false `FALSE`; query an explicit `category` to get a real
+  answer.}
 
 \item{complete}{If `TRUE`, fill the requested grid so that a cell the
   corpus does not carry still appears, labelled with **why** it is