filter projects by tag API parameter (#1222)

## Description

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:ticket: [TF-31754]

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[SPE-1234]:
https://hashicorp.atlassian.net/browse/SPE-1234?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQ
[TF-31754]:
https://hashicorp.atlassian.net/browse/TF-31754?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQ

Author: brandonc

content/terraform-docs-common/docs/cloud-docs/api-docs/changelog.mdx

@@ -9,6 +9,9 @@ description: >-
 
 Keep track of changes to the API for HCP Terraform and Terraform Enterprise.
 
+## 2025-10-31
+* Document API filtering parameters when [`listing projects`](/terraform/cloud-docs/api-docs/projects)
+
 <!-- BEGIN: TFC:only name:hcp-eu -->
 
 ## 2025-9-30

content/terraform-docs-common/docs/cloud-docs/api-docs/projects.mdx

@@ -334,6 +334,8 @@ This endpoint supports pagination [with standard URL query parameters](/terrafor
 | `filter[permissions][create-workspace]` | **Optional.** If present, returns a list of projects that the authenticated user can create workspaces in.                                                                                                                                                          |
 | `filter[permissions][move-stack]`       | **Optional.** If present, returns a list of projects that the authenticated user can move Stacks between. Only available in HCP Terraform.                                                                                                                                                          |
 | `filter[permissions][update]`           | **Optional.** If present, returns a list of projects that the authenticated user can update.                                                                                                                                                                        |
+| `filter[tagged][i][key]`                | **Optional.** If specified, restricts results to projects that are tagged with the provided key. Use a value of `"0"` for `i` if you are only using a single filter. For multiple tag filters, use an incrementing integer value for each filter. HCP Terraform combines multiple tag filters with a logical `AND` when filtering results. |
+| `filter[tagged][i][value]`              | **Optional.** If specified, restricts results to projects that are tagged with the provided value. This is useful when combined with a `key` filter for more specificity. Use a value of `"0"` for `i` if you are only using a single filter. For multiple tag filters, use an incrementing integer value for each filter. HCP Terraform combines multiple tag filters with a logical `AND` when filtering results. |
 | `sort`                                  | **Optional.** Allows sorting the organization's projects by `"name"`. Prepending a hyphen to the sort parameter reverses the order. For example, `"-name"` sorts by name in reverse alphabetical order. If omitted, the default sort order is arbitrary but stable. |
 
 ### Sample Request