Eng 2679 phase 6 documentation for terraform aws source module (#3960)

Re-do https://github.com/overmindtech/workspace/pull/3959 as the change
was merged out of order and got lost in rebasing; this depends on
https://github.com/overmindtech/workspace/pull/3958 getting merged
first.

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Low Risk**
> Documentation and workflow tooling changes only; no runtime code paths
or security-sensitive logic are modified.
>
> **Overview**
> Updates Terraform AWS source module documentation and publishing
references to use the new registry address
`overmindtech/aws-source/overmind`, and adds clearer module
development/testing guidance.
>
> Adds customer-facing docs at
`docs.overmind.tech/docs/sources/aws/terraform.md`, expands the module
README with import instructions, and introduces
`aws-source/module/.cursor/BUGBOT.md` review rules to keep IAM policy
changes read-only and Terraform provider errors using
`diag.Diagnostics`.
>
> Enhances `.cursor/commands/open-pull-request.md` to capture an
approved plan from Linear tickets and require a PR section explicitly
documenting *deviations from the approved plan*.
>
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
9356970fb0d18ac929d804484030d0cafa6621f5. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

GitOrigin-RevId: 1a5dc90ab5d93ecf70bf377cf58172a34f763314

Author: DavidS-ovm

README.md

@@ -18,7 +18,7 @@ provider "aws" {
 }
 
 module "overmind_aws_source" {
-  source = "overmindtech/aws-source-setup/overmind"
+  source = "overmindtech/aws-source/overmind"
 
   name = "production"
 }
@@ -41,7 +41,7 @@ module "overmind_aws_source" {
 | `source_id` | UUID of the Overmind source |
 | `external_id` | AWS STS external ID used in the trust policy |
 
-## Multi-account example
+## Multi-Account Example
 
 Use AWS provider aliases to onboard several accounts at once:
 
@@ -61,7 +61,7 @@ provider "aws" {
 }
 
 module "overmind_production" {
-  source = "overmindtech/aws-source-setup/overmind"
+  source = "overmindtech/aws-source/overmind"
   name   = "production"
 
   providers = {
@@ -71,7 +71,7 @@ module "overmind_production" {
 }
 
 module "overmind_staging" {
-  source  = "overmindtech/aws-source-setup/overmind"
+  source  = "overmindtech/aws-source/overmind"
   name    = "staging"
   regions = ["eu-west-1"]
 
@@ -82,6 +82,20 @@ module "overmind_staging" {
 }
 ```
 
+## Importing Existing Sources
+
+If you already created an Overmind AWS source through the UI and want to manage it
+with Terraform, you can import it using the source UUID (visible on the source
+details page in [Settings > Sources](https://app.overmind.tech/settings/sources)):
+
+```shell
+terraform import module.overmind_aws_source.overmind_aws_source.this <source-uuid>
+```
+
+After importing, run `terraform plan` to verify the state matches your
+configuration. Terraform will show any drift between the imported resource and
+your HCL.
+
 ## Authentication
 
 The Overmind provider reads `OVERMIND_API_KEY` from the environment. The API key

examples/multi-account/main.tf

@@ -19,7 +19,7 @@ provider "aws" {
 }
 
 module "overmind_production" {
-  source = "overmindtech/aws-source-setup/overmind"
+  source = "overmindtech/aws-source/overmind"
   name   = "production"
 
   providers = {
@@ -29,7 +29,7 @@ module "overmind_production" {
 }
 
 module "overmind_staging" {
-  source  = "overmindtech/aws-source-setup/overmind"
+  source  = "overmindtech/aws-source/overmind"
   name    = "staging"
   regions = ["eu-west-1"]
 

examples/single-account/main.tf

@@ -5,7 +5,7 @@ provider "aws" {
 }
 
 module "overmind_aws_source" {
-  source = "overmindtech/aws-source-setup/overmind"
+  source = "overmindtech/aws-source/overmind"
 
   name = "production"
 }