perf(build-newer-r): skip packages that already have a binary in bulk

Decide the already-built candidates from one listing per slot and one ABI-verdict query instead of a DB connection and several S3 requests per package; anything undecidable still goes through bincraft.

local/newer-r-helpers.R

@@ -73,3 +73,42 @@ newer_r_candidates <- function(db, primary_r, target_r) {
   result <- db[selected, c("Package", "Version"), drop = FALSE]
   result[order(result$Package), , drop = FALSE]
 }
+
+# Candidates that still need a build, decided from one bucket listing per slot
+# instead of a metadata-DB connection and several S3 requests per package.
+#
+# Mirrors bincraft's own skip decision: a package is done when a binary sits at
+# the path its cached ABI verdict routes it to, `<slot>/<minor>/` when
+# r-minor-sensitive and the flat `<slot>/` otherwise. A CRAN source sitting at
+# that key is a fallback, not a binary (see outstanding_packages()). Whatever
+# this cannot decide, no cached verdict or a slot that could not be listed,
+# stays in the list, so bincraft makes that call exactly as before.
+#
+# `sensitive`    cached verdicts for the current classifier, named `<pkg>_<ver>`
+# `flat_etags`   listing of the flat slot as for outstanding_packages(), or
+#                NULL when it could not be listed
+# `minor_etags`  the same for this interpreter's per-minor slot
+newer_r_outstanding <- function(
+  pkgs,
+  sensitive,
+  flat_etags,
+  minor_etags,
+  cran_md5
+) {
+  verdict <- unname(sensitive[paste(pkgs$Package, pkgs$Version, sep = "_")])
+  version <- stats::setNames(pkgs$Version, pkgs$Package)
+  keep <- rep(TRUE, nrow(pkgs))
+  routes <- list(
+    list(sensitive = FALSE, etags = flat_etags),
+    list(sensitive = TRUE, etags = minor_etags)
+  )
+  for (route in routes) {
+    idx <- which(verdict %in% route$sensitive)
+    if (length(idx) == 0L || is.null(route$etags)) {
+      next
+    }
+    keep[idx] <- pkgs$Package[idx] %in%
+      outstanding_packages(pkgs$Package[idx], route$etags, version, cran_md5)
+  }
+  pkgs[keep, , drop = FALSE]
+}