ci: multi-platform R CMD check for the GitHub mirror

The canonical Gitea runner is Linux-only, and this package hard-depends on
duckdb and httr2 -- both compiled, both with real platform variance --
while having never been checked on Windows or macOS. A large share of the
audience is on Windows.

Inert here: Gitea reads .gitea/workflows, GitHub reads .github/workflows,
so both configs coexist and the Gitea CI stays authoritative for deploys.
This goes live the moment the mirror repo exists (#44).

The matrix needs no credentials -- setup.R points at the bundled fixture --
which is why that fixture must never be .Rbuildignore'd.

.github/workflows/R-CMD-check.yaml

@@ -0,0 +1,61 @@
+# Multi-platform R CMD check, running on the GitHub mirror.
+#
+# This exists because the canonical Gitea runner is Linux-only, and this
+# package hard-depends on duckdb and httr2 -- both compiled, both with real
+# platform variance -- while having never been checked on Windows or macOS.
+# A large share of the audience is on Windows.
+#
+# Gitea reads .gitea/workflows and GitHub reads .github/workflows, so this
+# file is inert on the canonical repo and coexists with the Gitea CI that
+# remains authoritative for deploys.
+#
+# The suite needs NO credentials: tests/testthat/setup.R points USCOGDATA_URL
+# at the bundled fixture corpus. That is exactly why inst/extdata/fixture_corpus
+# must never be added to .Rbuildignore.
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+name: R-CMD-check
+
+permissions: read-all
+
+jobs:
+  R-CMD-check:
+    runs-on: ${{ matrix.config.os }}
+    name: ${{ matrix.config.os }} (${{ matrix.config.r }})
+
+    strategy:
+      fail-fast: false
+      matrix:
+        config:
+          - {os: macos-latest,   r: 'release'}
+          - {os: windows-latest, r: 'release'}
+          - {os: ubuntu-latest,  r: 'devel', http-user-agent: 'release'}
+          - {os: ubuntu-latest,  r: 'release'}
+
+    env:
+      GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}
+      R_KEEP_PKG_SOURCE: yes
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: r-lib/actions/setup-pandoc@v2
+
+      - uses: r-lib/actions/setup-r@v2
+        with:
+          r-version: ${{ matrix.config.r }}
+          http-user-agent: ${{ matrix.config.http-user-agent }}
+          use-public-rspm: true
+
+      - uses: r-lib/actions/setup-r-dependencies@v2
+        with:
+          extra-packages: any::rcmdcheck
+          needs: check
+
+      - uses: r-lib/actions/check-r-package@v2
+        with:
+          upload-snapshots: true
+          build_args: 'c("--no-manual")'

inst/extdata/fixture_corpus/manifest.json

@@ -1,7 +1,7 @@
 {
   "schema_version": 6,
-  "built_at": "2026-07-31T00:47:27Z",
+  "built_at": "2026-08-03T16:51:32Z",
-  "pipeline_commit": "aadb46b",
+  "pipeline_commit": "e7394a4",
   "fixture_note": "Four-year (2011, 2012, 2019, 2020) fixture for uscogdata tests. Full corpus available via USCOGDATA_URL. Regenerated from the sparsified schema-v6 corpus: the wide era (<= FY2011) no longer stores explicit zeros, so FY2011 absence means Census published $0 while FY2012+ absence means not reported. representation.parquet and code_set.parquet carry that rule and ship in full, as do every other metadata table in the publish tree. 2011/2012 straddle both the wide-aggregate -> modern-leaf format boundary (exercised by basis=\"harmonized\" and recipe= queries) and the dense -> sparse representation boundary (SB194); 2019/2020 retain the prior per-capita/CPI regression anchors. Regenerated via data-raw/regenerate_fixture_corpus.R.",
   "data_vintage": {
     "source_vintages": {
@@ -105,7 +105,7 @@
       },
       {
         "path": "data/series_breaks.parquet",
-        "sha256": "06dcc995ff533e57cc65fa25086cc9bf83ba592c58bf7cc99269dc2576f69944",
+        "sha256": "731998516cd802f63fcf7fb66053c7a62b7be955ab0794cad4a4979cb7628b87",
         "description": "series_breaks.parquet"
       },
       {