chore: regenerate fixture corpus with the intergovernmental category rows

Picks up pipeline PR #59: summary_categories now carries 66 M/L rows under
spend_subtype = intergovernmental (194 -> 260 rows).

cog_categories() (R/categories.R) has no item-code prefix filter, so the new
IG rows surface immediately as a third spend subtype; this broke
test-categories.R:18's closed enumeration. Adjudicated (2026-07-27): this is
correct behavior, not a regression -- cog_categories() is a discovery verb
documented to surface valid category values, and after Task 3 lands users
will see spend_subtype = intergovernmental in cog_spending(expenditure_concept
= total) results. Widened the subtype assertion and added positive coverage
asserting the intergovernmental subtype and that it reuses existing functional
categories (plus Other Education, pipeline #58). R/categories.R itself is
unchanged -- its behavior was already right.

Suite: PASS 469, FAIL 0 (baseline 467 + widened assertion + 2 new
expectations).

tests/testthat/test-categories.R

@@ -15,7 +15,18 @@ test_that("cog_categories(type = 'spending') returns only expenditure rows", {
   skip_if_no_corpus()
   r <- cog_categories(type = "spending")
   expect_true(all(r$category_type == "expenditure"))
-  expect_true(all(r$subtype %in% c("operations", "capital")))
+  expect_true(all(r$subtype %in% c("operations", "capital", "intergovernmental")))
+})
+
+test_that("cog_categories surfaces the intergovernmental spending subtype", {
+  skip_if_no_corpus()
+  r <- cog_categories(type = "spending")
+  expect_true("intergovernmental" %in% r$subtype)
+  # IG rows reuse the existing functional categories -- they add a subtype,
+  # not new category values.
+  ig_cats     <- sort(unique(r$category[r$subtype == "intergovernmental"]))
+  direct_cats <- sort(unique(r$category[r$subtype != "intergovernmental"]))
+  expect_true(all(ig_cats %in% c(direct_cats, "Other Education")))
 })
 
 test_that("cog_categories(type = 'revenue') returns only revenue rows", {