### Summary
This is a large refactor of the content for the LangGraph Platform
deployment options. Although there are a lot of changes, I do feel
fairly confident that this is safe to merge and won't have any negative
impact related to confusion around deployment options. However, please
review thoroughly (i.e. run the docs locally).
### Goals and Non-Goals
Just wanted to explicitly state goals and non-goals so that we're clear
about what needs to be done now versus what can be done in a smaller
follow-up PR.
Goals
1. Add new content for the new deployment options (Self-Hosted Data
Plane, Self-Hosted Control Plane).
1. Hide old content for deprecated deployment options (BYOC).
1. Create a pair of "conceptual" and "how-to" pages for each deployment
option. As much as possible, the pages should have consistent headings.
1. Introduce the terms "control plane" and "data plane" and define them
plainly without hiding/abstracting information.
Non-Goals
1. Do not change the navigation of the existing deployment options. As
much as possible, update content in-place or add new pages. Changing the
navigation is a bigger task that can be done later.
1. Do not remove old content for deprecated deployment options. We may
need to refer to this later. There are only ~2 pages (I think).
### Next Steps
1. Update the architecture diagrams for each deployment option. Commit
Excalidraw file to source control.
1. Create a "how-to" page for the Control Plane UI. This page pertains
to 3/4 deployment options. Most of the content lives in the "how-to"
page for Cloud SaaS deployment.
1. Document required RBAC permissions for K8s for Self-Hosted Data Plane
and Self-Hosted Control Plane (and update links).
1. Figure out how to consolidate plan information.
1. Figure out where to document licensing, telemetry, custom
Postgres/Redis.
1. Update autoscaling content.
Plus:
1. Improve docstrings of add_node
2. Update crosslinking of sqlite and aiosqlite docstrings
3. Fix a bunch of links so we can turn on strict validation
* 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.
