docs: Various updates to LangGraph Cloud docs (#805)

* Change LangGraph Deploy to LangGraph Cloud in CLI reference.

* Update main README to link to Cloud docs. Update How-to Guide link in Cloud index page.

* Create Environments Variable reference page.

* Add Authentication to Conceptual Guide.

* Update setup how-to to refer back to CompiledGraph variable name.

* Update how-to notebooks for double texting.

* Add warning about setting top-level variable for CompiledGraph.

examples/cloud_examples/enqueue_concurrent.ipynb

@@ -6,7 +6,9 @@
    "source": [
     "## Enqueue\n",
     "\n",
-    "There are several strategies for handling concurrent runs in your graph. This notebook covers how to use the `enqueue` option - please see the other how-to guides in the \"Double Texting\" directory to learn about the other methods.\n",
+    "This notebook assumes knowledge of what double-texting is, which you can learn about in the [double-texting conceptual guide](https://langchain-ai.github.io/langgraph/cloud/concepts/#double-texting).\n",
+    "\n",
+    "The guide covers the `enqueue` option for double texting, which adds the interruptions to a queue and executes them in the order they are received by the client. Below is a quick example of using the `enqueue` option.\n",
     "\n",
     "First, let's import our required packages and instantiate our client, assistant, and thread."
    ]

examples/cloud_examples/interrupt_concurrent.ipynb

@@ -6,7 +6,9 @@
    "source": [
     "## Interrupt\n",
     "\n",
-    "There are several strategies for handling concurrent runs in your graph. This notebook covers how to use the `interrupt` option - please see the other how-to guides in the \"Double Texting\" directory to learn about the other methods.\n",
+    "This notebook assumes knowledge of what double-texting is, which you can learn about in the [double-texting conceptual guide](https://langchain-ai.github.io/langgraph/cloud/concepts/#double-texting).\n",
+    "\n",
+    "The guide covers the `interrupt` option for double texting, which interrupts the prior run of the graph and starts a new one with the double-text. This option does not delete the first run, but rather keeps it in the database but sets its status to `interrupted`. Below is a quick example of using the `interrupt` option.\n",
     "\n",
     "First, let's import our required packages and instantiate our client, assistant, and thread."
    ]

examples/cloud_examples/reject_concurrent.ipynb

@@ -6,7 +6,9 @@
    "source": [
     "## Reject\n",
     "\n",
-    "There are several strategies for handling concurrent runs in your graph. This notebook covers how to use the `reject` option - please see the other how-to guides in the \"Double Texting\" directory to learn about the other methods.\n",
+    "This notebook assumes knowledge of what double-texting is, which you can learn about in the [double-texting conceptual guide](https://langchain-ai.github.io/langgraph/cloud/concepts/#double-texting).\n",
+    "\n",
+    "The guide covers the `reject` option for double texting, which rejects the new run of the graph by throwing an error and continues with the original run until completion. Below is a quick example of using the `reject` option.\n",
     "\n",
     "First, let's import our required packages and instantiate our client, assistant, and thread."
    ]

examples/cloud_examples/rollback_concurrent.ipynb

@@ -6,7 +6,9 @@
    "source": [
     "## Rollback\n",
     "\n",
-    "There are several strategies for handling concurrent runs in your graph. This notebook covers how to use the `rollback` option - please see the other how-to guides in the \"Double Texting\" directory to learn about the other methods.\n",
+    "This notebook assumes knowledge of what double-texting is, which you can learn about in the [double-texting conceptual guide](https://langchain-ai.github.io/langgraph/cloud/concepts/#double-texting).\n",
+    "\n",
+    "The guide covers the `rollback` option for double texting, which interrupts the prior run of the graph and starts a new one with the double-text. This option is very similar to the `interrupt` option, but in this case the first run is completely deleted from the database and cannot be restarted. Below is a quick example of using the `rollback` option.\n",
     "\n",
     "First, let's import our required packages and instantiate our client, assistant, and thread."
    ]