Add type filter and facet counts to the search endpoint

The search JSON gains tab support: the new `filter` GET parameter
restricts results to one document type (product, news, download, story,
page, market); the response carries `filter` (active value or null) and
`facets.type` with per-type counts and active flags. Counts stay
complete while a filter is active (keepAllFacetsOnSelection), so tabs
never collapse - except on an empty filtered result, documented in spec
v1.12 clause 7.16.

The parameter is named `filter` because `type` is TYPO3's reserved
page-type parameter and crashes page resolution; like q and page it is
excluded from cHash validation. Facets come from EXT:solr's native
faceting, serialized generically by SearchJsonRenderer - a future
category facet only needs TypoScript.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

packages/vitec/Configuration/Sets/Vitecset/setup.typoscript

@@ -533,3 +533,19 @@ plugin.tx_solr.index.queue {
         }
     }
 }
+
+# Type facet for the search JSON: counts per document type, serialized by
+# SearchJsonRenderer as content.search.facets.type. keepAll* keeps the full
+# counts visible while one type is selected - otherwise the tabs would
+# collapse to the active one.
+plugin.tx_solr.search.faceting = 1
+plugin.tx_solr.search.faceting {
+    keepAllFacetsOnSelection = 1
+    facets {
+        type {
+            label = Type
+            field = type
+            keepAllOptionsOnSelection = 1
+        }
+    }
+}