Expose which search strategy produced each result

query_packages now assigns @search_sources - a hash mapping package
ids to the matching strategy that put them into the results: :exact,
:name_prefix, :name_contains, :semantic or :fulltext. The grid and
list views render a small badge with a humanized label per result,
making the search tiers observable. semantic_results() was folded
into search_packages() so each branch tags its own source. Adds the
rails-controller-testing gem for assigns() in tests.

Gemfile.lock

@@ -381,6 +381,10 @@ GEM
       activesupport (= 8.1.3)
       bundler (>= 1.15.0)
       railties (= 8.1.3)
+    rails-controller-testing (1.0.5)
+      actionpack (>= 5.0.1.rc1)
+      actionview (>= 5.0.1.rc1)
+      activesupport (>= 5.0.1.rc1)
     rails-dom-testing (2.3.0)
       activesupport (>= 5.0.0)
       minitest
@@ -592,6 +596,7 @@ DEPENDENCIES
   propshaft
   puma (>= 5.0)
   rails (~> 8.1.0)
+  rails-controller-testing
   rails-erd
   rails-healthcheck
   rails_icons (~> 1.3)