Deduplicate search results by package name

If the database ever contains duplicate-name rows again, users should
not see the same package twice in the results.

app/controllers/packages_controller.rb

@@ -425,7 +425,10 @@ class PackagesController < ApplicationController
       logger.debug "Query '#{query}' has no lexical overlap with package data"
     end
 
-    results = (prefix_matches + token_matches + semantic).uniq(&:id)
+    # Deduplicate by NAME, not id: if the database ever contains
+    # duplicate rows (see the packages_name_key incident) users should
+    # not see the same package twice.
+    results = (prefix_matches + token_matches + semantic).uniq(&:name)
 
     # Queries that share no vocabulary with our package data can produce
     # no meaningful results. Skip the vector service round-trip and show