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.

R/provenance.R

@@ -67,7 +67,15 @@
     basis_note = basis_note,
     expenditure_concept = expenditure_concept,
     expenditure_concept_note = expenditure_concept_note,
-    expenditure_concept_direct_suppressed = isTRUE(expenditure_concept_direct_suppressed),
+    # isTRUE() alone would collapse a deliberate NA (all-categories mode,
+    # where suppression detection cannot run -- see .verb_spendrev()) down to
+    # FALSE, turning "we don't know" back into the false claim this field
+    # exists to avoid. Preserve NA; otherwise normalize to a strict logical.
+    expenditure_concept_direct_suppressed = if (isTRUE(is.na(expenditure_concept_direct_suppressed))) {
+      NA
+    } else {
+      isTRUE(expenditure_concept_direct_suppressed)
+    },
     revenue_concept = revenue_concept,
     harmonization = harmonization %||% list(
       applied = FALSE, na_rows_excluded = 0L, na_amount_excluded = 0,