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/schemas/provenance-v1.json

@@ -14,16 +14,16 @@
     "basis_note":     { "type": ["string", "null"] },
     "expenditure_concept": {
       "type": "string",
-      "enum": ["direct", "total"],
-      "description": "Which spending concept produced this result. 'direct' is the government's own E/F/G spending; 'total' adds its intergovernmental payments (M to local governments, L to state governments). Only 'direct' is valid for results combined across governments."
+      "enum": ["primary", "direct", "total"],
+      "description": "Which spending concept produced this result, defined as crosswalk spend_subtype sets (never item-code prefixes). 'primary' (the default) is the government's own service provision: operations + capital + assistance. 'direct' adds interest on debt and insurance trust benefit payments (Census's published Direct Expenditure). 'total' adds intergovernmental payments (M to local governments, L to state government, Q11/Q12/Q18 to school systems). Only 'primary' and 'direct' are valid for results combined across governments."
     },
     "expenditure_concept_note": {
       "type": ["string", "null"],
-      "description": "How the intergovernmental leg was assembled; null for 'direct'."
+      "description": "How the intergovernmental leg was assembled; null for 'primary' and 'direct'."
     },
     "expenditure_concept_direct_suppressed": {
       "type": "boolean",
-      "description": "TRUE when expenditure_concept = 'total' and at least one requested (year, category) has intergovernmental rows but NO Direct rows in this corpus (typically a legacy aggregate-only family) -- those result rows report the intergovernmental leg alone, not Direct + IG. Always FALSE for expenditure_concept = 'direct'. See the affected rows' `notes` for the recovering recipe, if any."
+      "description": "TRUE when expenditure_concept = 'total' and at least one requested (year, category) has intergovernmental rows but NO Direct rows in this corpus (typically a legacy aggregate-only family) -- those result rows report the intergovernmental leg alone, not Direct + IG. Always FALSE for expenditure_concept = 'primary' or 'direct'. See the affected rows' `notes` for the recovering recipe, if any."
     },
     "harmonization":  { "type": "object" },
     "recipe":         { "type": ["object", "null"] },