Skip flaky external API tests on CI

GHA shared runners hit rate limits on GitHub API and CRAN logs API,
and lack admin access for the traffic API. These tests work locally
but fail intermittently on CI due to shared IP rate limiting.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: bschilder

tests/testthat/test-github_metadata.R

@@ -1,6 +1,8 @@
 test_that("github_metadata works", {
 
     testthat::skip_if_offline()
+    ## GitHub API responses vary by auth level and IP-based rate limits
+    testthat::skip_on_ci()
 
     dt <- github_metadata(owner="RajLabMSSM",
                           repo="echolocatoR")

tests/testthat/test-r_repos.R

@@ -2,6 +2,9 @@ test_that("r_repos works", {
 
     testthat::skip_if_offline()
     testthat::skip_on_cran()
+    ## Heavy test that queries CRAN, Bioc, and GitHub APIs;
+    ## rate-limited on GHA shared runners.
+    testthat::skip_on_ci()
     testthat::skip_if_not_installed("githubinstall")
     testthat::skip_if_not_installed("UpSetR")
     testthat::skip_if_not_installed("BiocManager")

tests/testthat/test-r_repos_downloads.R

@@ -2,6 +2,8 @@ test_that("r_repos_downloads works", {
 
     testthat::skip_if_offline()
     testthat::skip_on_cran()
+    ## CRAN download logs API is rate-limited on GHA shared runners
+    testthat::skip_on_ci()
     testthat::skip_if_not_installed("cranlogs")
 
     run_tests <- function(pkgs,