docs(cookbook): defer nav placement, leave Cookbook section orphaned

Remove the root and learn meta.json entries that placed the Cookbook in the
docs sidebar / Learn footer, deferring the nav-placement decision (top-level
tab vs sidebar group) to a follow-up. The recipe pages still route at
/cookbook and /cookbook/daytona (Fumadocs discovers MDX from the filesystem,
confirmed via .source generation), so Daytona-side deeplinks continue to
work. Nothing in our docs nav points at the section until the decision lands.

Also drops the stale '[Cookbook: State Machine]' Learn entry entirely (it had
been temporarily repointed to /cookbook in the previous commit).

OSS-222

Author: contextablemark

docs/content/docs/learn/meta.json

@@ -20,7 +20,6 @@
     "...tutorials",
     "[Tutorial: AI Todo App](../direct-to-llm/tutorials/ai-todo-app/overview)",
     "[Tutorial: AI Travel App](../langgraph/tutorials/ai-travel-app)",
-    "[Video: Research Canvas](../langgraph/videos/research-canvas)",
-    "[Cookbook](../cookbook)"
+    "[Video: Research Canvas](../langgraph/videos/research-canvas)"
   ]
 }

docs/content/docs/meta.json

@@ -5,7 +5,6 @@
     "...(root)",
     "reference",
     "learn",
-    "cookbook",
     "---Integrations---",
     "...integrations",
     "a2a",