fix: regenerate the bundled fixture against the sparsified corpus (#18)

The fixture predated three shipped corpus changes at once: no J rows in
summary_categories (it was built before the crosswalk completion), no
representation.parquet or code_set.parquet, and a still-dense wide era.
Every test in this package and in cog-api runs against it, so both suites
were green against a corpus that no longer exists. This is #18's stated
prerequisite; it proves nothing about production until it lands.

Regenerated from the publish tree at pipeline_commit 83f9715 (schema v6,
built 2026-07-29). FY2011 goes from 2,864,212 rows to 496,004 -- 82.7% of
the old partition was explicit zeros -- and the fixture now ships all ten
publish-tree metadata tables rather than six. The generator's file list is
a single constant now, so the copy step and the manifest step cannot drift.

Three test repairs, each a real consequence of sparsification rather than
a number to bump:

  test-categories.R          "assistance" joined the spending subtype
                             vocabulary with the J-prefix codes.

  test-spending.R            The harmonization block counts rows that
                             exist. Broward's E21/F21/G21 were zero-pads
                             and are gone, so the anchor moves to FL state,
                             whose three NA-mapped rows carry $2.83B --
                             the amount accounting was previously asserted
                             only against 0 and could not have caught a
                             bug. Broward keeps a test of its own, now
                             asserting the zero-pads are absent.

  test-expenditure-concept.R Coverage-gap suggestions are presence-based.
                             AL state's only FY2011 B47 cell was an
                             explicit zero, so ig_federal_b47_wide stopped
                             being a candidate there; FL state carries a
                             real amount, so the counterpart guard is
                             exercised against a suggestion that fires.

test-fixture-vintage.R pins the structural facts that separate this vintage
from its predecessor -- the ten metadata tables, the dense/sparse
representation contract, zero explicit zeros in FY2011, code_set coverage,
and J19's category. Checked against the old fixture: FY2011 carried
2,368,208 explicit zeros, so the assertion discriminates rather than
merely passing.

Suites: uscogdata 594 pass / 0 fail / 6 skip (was 576/0/6).
cog-api 357 pass / 0 fail / 8 skip against the regenerated fixture,
unchanged from its baseline.

tests/testthat/test-categories.R

@@ -15,7 +15,11 @@ 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", "intergovernmental")))
+  # "assistance" (the J-prefix aid/benefit codes) joined the vocabulary with
+  # the crosswalk completion in cog_pipeline#60/#65 -- every flow code
+  # carrying dollars now maps to a category.
+  expect_true(all(r$subtype %in%
+                  c("operations", "capital", "intergovernmental", "assistance")))
 })
 
 test_that("cog_categories surfaces the intergovernmental spending subtype", {