fix: address Task 3 code review (bool_or, invariant tests, guards, docs)

Nine review items on the expenditure_concept = direct|total feature:

- bool_and(is_aggregate) -> bool_or(is_aggregate) for aggregate_fallback:
  bool_and silently misreported $5,740,775,000 of aggregate-sourced IG
  dollars (AL state 2011) as aggregate_fallback = FALSE, because the dense
  wide-era data puts a $0 leaf row in the same group as the real aggregate
  row. bool_or is a no-op for Direct/Revenue (verified: 0 mismatched groups
  across both tables) and correct for the IG leg.
- Added a year-disjointness invariant test for the four legacy
  aggregate/leaf IG pairs (M47/M94, M89/M91-93, L47/L94, L89/L91-93),
  scoped to the aggregate flag rather than bare code presence (M89/L89
  continue past 2011 as independent, non-aggregate leaves).
- Extended the real-SQL-text/synthetic-parquet harness in test-views.R to
  pin ig_long/ig_long_harmonized's predicates directly (aggregate rows
  retained, NULL harmonized_code coalesced, L-- excluded), rather than
  relying on one fixture row's incidental shape.
- Added a test proving the .harmonization_view_files schema-v5 guard is
  necessary (not just incidental) against a corpus whose `long` genuinely
  lacks a harmonized_code column, and rewrote the misleading "v5-only
  parquet files" comment to name both real reasons a file is gated.
- Fixed an NA-fragile subtype filter, extended the expected-view-list
  test, guarded .verb_spendrev() against total on a non-spending
  view_base, added a roxygen caveat against summing total across levels
  of government, and replaced an uncheckable corpus-wide SQL comment
  figure with a fixture-verifiable one.

Full suite: 485/0/0 -> 503/0/0 (18 new expectations, zero pre-existing
value changed).

man/cog_spending.Rd

@@ -64,7 +64,12 @@ intergovernmental leg -- payments to local governments (`M` codes) and
 to the state government (`L` codes, excluding the `L--` family-total
 rollup) -- so results gain rows with `spend_subtype ==
 "intergovernmental"`. Mutually exclusive with `recipe` (a recipe
-already defines its own component codes).}
+already defines its own component codes). **Do not sum `"total"`
+results across levels of government** (e.g. state + county + city):
+a state's `M12` payment to a school district is the same dollar the
+district reports as its own direct `E12`, so summing both double-counts
+it. This matters in particular with [cog_geographic_rollup()], which
+sums across exactly that kind of multi-layer government set.}
 }
 \value{
 Tibble with columns `year`, `canonical_govid`, `gov_name`,