feat(patches): add registry validator script

local/validate-patches.R

@@ -0,0 +1,51 @@
+#!/usr/bin/env Rscript
+# Validate local/patches/registry.json: schema, referenced patch files, and
+# ambiguous overlaps. Exits 1 on any problem. Used by pre-commit and CI.
+
+dir <- "local/patches"
+registry_file <- file.path(dir, "registry.json")
+if (!file.exists(registry_file)) {
+  cat("No registry.json found; nothing to validate.\n")
+  quit(status = 0L)
+}
+
+reg <- jsonlite::fromJSON(registry_file, simplifyVector = FALSE)
+required <- c("package", "versions", "platforms", "reason")
+errs <- character(0L)
+
+for (i in seq_along(reg)) {
+  e <- reg[[i]]
+  missing <- setdiff(required, names(e))
+  if (length(missing) > 0L) {
+    errs <- c(errs, sprintf(
+      "entry %d (%s): missing %s", i,
+      if (is.null(e$package)) "?" else e$package, toString(missing)
+    ))
+  }
+  if (!is.null(e$patch)) {
+    p <- file.path(dir, e$patch)
+    if (!file.exists(p)) {
+      errs <- c(errs, sprintf("entry %d (%s): patch file '%s' missing",
+                              i, e$package, p))
+    }
+  }
+}
+
+# Ambiguous overlap: two entries for the same package with identical platforms
+# and versions.
+keys <- vapply(reg, function(e) {
+  sprintf("%s|%s|%s", e$package,
+          paste(sort(as.character(unlist(e$platforms))), collapse = ","),
+          e$versions)
+}, character(1L))
+dups <- keys[duplicated(keys)]
+if (length(dups) > 0L) {
+  errs <- c(errs, sprintf("ambiguous duplicate entries: %s", toString(unique(dups))))
+}
+
+if (length(errs) > 0L) {
+  cat("Patch registry validation FAILED:\n")
+  cat(paste0("  - ", errs, "\n"))
+  quit(status = 1L)
+}
+cat(sprintf("Patch registry OK (%d entrie(s)).\n", length(reg)))