feat: three-concept expenditure model classified by crosswalk membership (#11)

Rewrites expenditure/revenue classification off item-code first-letter
prefixes and onto summary_categories membership (F-018: prefix Y spans
revenue, expenditure, and balance codes), and exposes
expenditure_concept = c("primary", "direct", "total") with primary as
the new default:

  primary = operations + capital + assistance
  direct  = primary + interest + insurance_benefits   (Census Direct)
  total   = direct + intergovernmental                (M/L/Q via ig views)

- inst/sql: flow views (20-25) select by crosswalk membership;
  summary_categories moves to 11- so it registers before them (DuckDB
  binds view sources eagerly). The IG leg gains Q11/Q12/Q18 state
  school-system payments (F-017).
- R: one subtype scope per verb call drives the verb SQL, the
  harmonization exclusion count, and the complete = TRUE grid;
  flow_prefixes survives only to scope recipe suggestions.
  cog_geographic_rollup/cog_peer_compare accept primary|direct, still
  refuse total, and now actually pass the concept through.
- Balance codes can never reach a spending or revenue result
  (uscogdata#25), asserted at both view and verb level.
- Deletes the #11 skip; per the 2026-07-30 owner ruling the F-018 Y01
  proof is asserted against the crosswalk, not the default
  cog_revenue() call (which stays General Revenue pending #12).

Suite: 696 pass / 0 fail / 1 skip (#12, expected).

Closes #11

inst/sql/20-spending_long.sql

@@ -1,5 +1,22 @@
+-- Direct-side expenditure rows, classified by crosswalk MEMBERSHIP
+-- (summary_categories.category_type = 'expenditure'), never by item-code
+-- first letter: prefix Y alone spans revenue (Y01/Y02), expenditure
+-- (Y05/Y06) and balance codes, so no first-letter allowlist can route it
+-- (uscogdata#11, finding F-018). Which subtypes a query actually returns is
+-- decided per expenditure_concept in R (.verb_spendrev); this view carries
+-- every non-intergovernmental expenditure subtype: operations, capital,
+-- assistance, interest, insurance_benefits.
+--
+-- The intergovernmental subtype (M/L/Q codes) is deliberately carved out
+-- into ig_long: its legacy-era rows are published ONLY as aggregate-flagged
+-- rows, so it cannot live behind this view's NOT is_aggregate filter (see
+-- 24-ig_long.sql).
 CREATE OR REPLACE VIEW spending_long AS
 SELECT *
 FROM long
-WHERE LEFT(item_code, 1) IN ('E', 'F', 'G')
+WHERE item_code IN (
+    SELECT item_code FROM summary_categories
+    WHERE category_type = 'expenditure'
+      AND spend_subtype <> 'intergovernmental'
+  )
   AND NOT is_aggregate;