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_balances.Rd

@@ -28,7 +28,12 @@ argument: for holdings, `category` is a strict coarsening of
 every combination would be either redundant or empty.
 `category = "Fund Balances"` is exactly the `general` family
 (`W01`/`W31`/`W61`). `balance_subtype` is returned, so a finer split is
-one `dplyr::filter()` away.}
+one `dplyr::filter()` away. The reserved pseudo-category
+`"All Categories"` (see [cog_spending()]) is **not** supported here and
+errors with class `uscogdata_all_categories_unsupported`: it sums a
+concept's subtype scope, and holdings are a stock with no concept
+vocabulary to sum across. Omit `category` to get every category broken
+out instead.}
 
 \item{per_capita}{Divide holdings by population. Note this is a **stock per
 resident** (reserves per person), which is *not* comparable to