docs: give SQL one section with a page per construct

SELECT and Enterprise SQL sat apart in Query while documenting the same engine.
They are now one SQL group: overview, Select, Aggregation, Join, Window,
Sampling, Functions -- one page per construct, with the Enterprise client-setup
and FTS pages merged in rather than parallel to them.

Sampling is new. TABLESAMPLE is implemented and was undocumented: BERNOULLI
picks rows, SYSTEM picks Lance fragments, REPEATABLE fixes the draw so a sample
works as a stable evaluation set. Its refusals are documented too -- a
percentage over 100, a fractional row count, BUCKET, the SAMPLE spelling and
the OFFSET modifier are all errors, because a sampling clause that were read and
not applied would be a wrong answer rather than a missing feature.

Schema & Data Types is one page again, with the multimodal content merged into
its blob section rather than sitting beside it.

Agentic Skills stops being a tab. Both its pages are tutorials, so they join the
Tutorials tab; the Basics page that introduces them stays.

docs/web/docs.json

@@ -55,10 +55,6 @@
       "source": "/catalog/database",
       "destination": "/basics/catalog"
     },
-    {
-      "source": "/sql",
-      "destination": "/basics/apis"
-    },
     {
       "source": "/api-reference",
       "destination": "/basics/apis"
@@ -74,6 +70,14 @@
     {
       "source": "/tables/create",
       "destination": "/ingestion"
+    },
+    {
+      "source": "/tables/multimodal",
+      "destination": "/basics/data-types#blob"
+    },
+    {
+      "source": "/search/select",
+      "destination": "/sql/select"
     }
   ],
   "navigation": {
@@ -94,13 +98,7 @@
               "basics/lance",
               "basics/catalog",
               "basics/jobs",
-              {
-                "group": "Schema & Data Types",
-                "pages": [
-                  "basics/data-types",
-                  "tables/multimodal"
-                ]
-              },
+              "basics/data-types",
               "tables/consistency",
               "basics/apis",
               "basics/agentic-skills"
@@ -145,15 +143,11 @@
             "group": "Query",
             "pages": [
               "search/index",
-              "search/select",
               "search/vector-search",
               "search/multivector-search",
               "search/full-text-search",
               "search/hybrid-search",
               "search/filtering",
-              "search/explain",
-              "search/explain-analyze",
-              "sql/functions",
               {
                 "group": "Reranking",
                 "pages": [
@@ -165,6 +159,20 @@
                   "reranking/custom-reranker",
                   "reranking/eval"
                 ]
+              },
+              "search/explain",
+              "search/explain-analyze",
+              {
+                "group": "SQL",
+                "pages": [
+                  "sql/index",
+                  "sql/select",
+                  "sql/aggregation",
+                  "sql/join",
+                  "sql/window",
+                  "sql/sampling",
+                  "sql/functions"
+                ]
               }
             ]
           },
@@ -329,6 +337,13 @@
               "training/vlm-finetuning"
             ]
           },
+          {
+            "group": "AI Agents",
+            "pages": [
+              "build-with-ai-agents",
+              "agent-branch-experiments"
+            ]
+          },
           {
             "group": "Robotics",
             "pages": [
@@ -356,18 +371,6 @@
             ]
           }
         ]
-      },
-      {
-        "tab": "Agentic Skills",
-        "groups": [
-          {
-            "group": "Agentic Skills",
-            "pages": [
-              "build-with-ai-agents",
-              "agent-branch-experiments"
-            ]
-          }
-        ]
       }
     ]
   },