docs: index all 14 exports in pkgdown, set the site url

The reference index covered 6 of 14 exports, so pkgdown errored on the
eight missing topics and the docs site did not build at all. Adds a
Comparison & aggregation section and a Corpus metadata section, lists both
vignettes as articles, and sets url so canonical links and search resolve.

build_site() now completes clean: reference metadata ok, no problems.

_pkgdown.yml

@@ -1,4 +1,5 @@
-url: ~
+url: https://civilytics.r-universe.dev/uscogdata
+
 template:
   bootstrap: 5
 
@@ -15,11 +16,26 @@ reference:
       - cog_gov_search
       - cog_basket_resolution
       - cog_basket_unresolved
-  - title: Session
+  - title: Comparison & aggregation
+    desc: Peer cohorts and geographic aggregates.
     contents:
-      - has_keyword("internal")
+      - cog_find_peers
+      - cog_peer_compare
+      - cog_geographic_rollup
+  - title: Corpus metadata
+    desc: >
+      What the corpus contains, where a given result came from, and how to
+      hold a local copy of it.
+    contents:
+      - cog_categories
+      - cog_recipes
+      - cog_manifest
+      - cog_explain
+      - cog_mirror
 
 articles:
-  - title: Getting started
+  - title: Concepts
     navbar: ~
-    contents: []
+    contents:
+      - total-spending
+      - population-denominators

tests/testthat/test-config.R

@@ -131,3 +131,17 @@ test_that("vignettes are not excluded from the build", {
   # r-universe and GitHub Actions. It must never be excluded.
   expect_false(any(grepl("fixture_corpus", ignore, fixed = TRUE)))
 })
+
+test_that("_pkgdown.yml indexes every exported topic", {
+  skip_if_no_source_tree("_pkgdown.yml", "NAMESPACE")
+  exports <- grep("^export\\(", readLines(source_tree_path("NAMESPACE"), warn = FALSE),
+                  value = TRUE)
+  exports <- sub("^export\\((.*)\\)$", "\\1", exports)
+  yml <- paste(readLines(source_tree_path("_pkgdown.yml"), warn = FALSE), collapse = "\n")
+  missing <- exports[!vapply(exports,
+                             function(e) grepl(paste0("\\b", e, "\\b"), yml),
+                             logical(1))]
+  # pkgdown errors on topics missing from the index, so an unlisted export
+  # means the docs site does not build at all.
+  expect_equal(missing, character(0))
+})