feat: all-categories mode in .build_verb_sql()

The concept boundary in this package is subtype, not category, so a
total is the existing query with the category dimension collapsed and
no category predicate applied. subtype is deliberately kept in the
grouping: subtype=operations plus all-categories is 'operating
expenditure', which is the measure a fiscal comparison wants.

Named 'All Categories' rather than 'Total' because category='Total'
would sit one argument from expenditure_concept='total' and mean
something different.

tests/testthat/test-all-categories.R

@@ -0,0 +1,39 @@
+# Baseline at branch point: 843 PASS / 0 FAIL / 0 SKIP / 0 WARN (2026-08-05, origin/main 2fc9e75)
+
+test_that(".build_verb_sql emits a literal category and no category filter in all-categories mode", {
+  sql <- uscogdata:::.build_verb_sql(
+    view         = "spending_annotated",
+    subtype_col  = "spend_subtype",
+    govid        = "552025209777",
+    years        = 2019L,
+    category     = NULL,
+    subtype_scope = c("operations", "capital"),
+    all_categories = TRUE
+  )
+
+  expect_match(sql, "'All Categories' AS category", fixed = TRUE)
+  # no category filter of any kind
+  expect_false(grepl("AND category IN", sql, fixed = TRUE))
+  # category is not a grouping key
+  expect_false(grepl("GROUP BY year, canonical_govid, gov_name, xwalk_gov_name, spend_subtype, category",
+                     sql, fixed = TRUE))
+  # the subtype allowlist still applies -- this is what makes the sum a concept
+  expect_match(sql, "AND spend_subtype IN ('operations','capital')", fixed = TRUE)
+})
+
+test_that(".build_verb_sql is unchanged when all_categories is FALSE", {
+  args <- list(
+    view = "spending_annotated", subtype_col = "spend_subtype",
+    govid = "552025209777", years = 2019L, category = NULL,
+    subtype_scope = c("operations", "capital")
+  )
+  old <- do.call(uscogdata:::.build_verb_sql, args)
+  new <- do.call(uscogdata:::.build_verb_sql, c(args, list(all_categories = FALSE)))
+  expect_identical(old, new)
+  expect_match(new, "GROUP BY year, canonical_govid, gov_name, xwalk_gov_name, spend_subtype, category",
+               fixed = TRUE)
+})
+
+test_that(".ALL_CATEGORIES is the exact reserved string", {
+  expect_identical(uscogdata:::.ALL_CATEGORIES, "All Categories")
+})