docs: split Query from Job, and fold the agent tutorial into Agentic Skills

Query and Job were one page because they share the _async convention, but they
are different things: a query returns rows and streams them, a job returns an
outcome you wait for. Two pages now, query first, each carrying a short pointer
to the other rather than the shared framing.

Agentic Skills absorbs the agent plugin tutorial, which was a separate page in
Use Cases describing the same plugin in more detail -- the two had diverged, with
the tutorial carrying the fuller install instructions. It also moves to Getting
Started: installing the plugin is something you do before writing anything, not
a concept to understand.

docs/web/docs.json

@@ -138,6 +138,10 @@
     {
       "source": "/training",
       "destination": "/training/data-loading"
+    },
+    {
+      "source": "/build-with-ai-agents",
+      "destination": "/basics/agentic-skills"
     }
   ],
   "navigation": {
@@ -150,7 +154,8 @@
             "pages": [
               "index",
               "quickstart",
-              "architecture"
+              "architecture",
+              "basics/agentic-skills"
             ]
           },
           {
@@ -158,12 +163,12 @@
             "pages": [
               "basics/lance",
               "basics/catalog",
+              "basics/query",
               "basics/jobs",
               "tables/consistency",
               "basics/guarantees",
               "basics/limits",
-              "basics/apis",
-              "basics/agentic-skills"
+              "basics/apis"
             ]
           },
           {
@@ -393,12 +398,6 @@
         "tab": "Use Cases",
         "pages": [
           "tutorials/index",
-          {
-            "group": "General",
-            "pages": [
-              "build-with-ai-agents"
-            ]
-          },
           {
             "group": "Search",
             "pages": [