Fork for Threshold: rename module, use Threshold api/sdk, rebrand docs, add CI

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

NOTICE

@@ -0,0 +1,15 @@
+terraform-provider-threshold
+
+This project is a community fork of terraform-provider-boundary
+(https://github.com/hashicorp/terraform-provider-boundary),
+Copyright (c) HashiCorp, Inc. / IBM Corp., licensed under the Mozilla Public
+License, version 2.0. The original copyright and license notices are retained in
+LICENSE and in the source file headers.
+
+Modifications in this fork (Go module path, imports of the Threshold api/sdk
+modules, product wording, removal of HashiCorp release tooling, CI) are made by
+CyberCove LLC and its contributors and are likewise made available under MPL-2.0.
+
+This fork is a community project for Threshold, a community fork of Boundary CE.
+It is not affiliated with, endorsed by, or supported by HashiCorp or IBM.
+"Boundary", "Terraform" and "HashiCorp" are trademarks of their respective owners.