Add configurable --tf-path for Terragrunt OpenTofu support

[Copilot]

Terragrunt's --tf-path parameter was hardcoded to "terraform", preventing users from using OpenTofu or other Terraform-compatible binaries.

Changes

Backend

• Added TfPath field to TerraformTemplateParams for storing the binary path
• Updated TerraformApp to use configurable path via getTfPath() helper (defaults to "terraform")
• Applied to all Terragrunt commands: init, workspace list/select, plan, apply

Frontend

• Added "Terraform binary path" input field to template settings (Terragrunt only)
• Configured field visibility, translation, and form constants

Usage

Users can now specify alternative binaries in Terragrunt template settings:

{
  "task_params": {
    "tf_path": "tofu"  // or "/usr/local/bin/tofu", or leave empty for "terraform"
  }
}

This generates commands like:

terragrunt init --tf-path=tofu
terragrunt plan --tf-path=tofu

Backward compatible: existing templates continue using "terraform" by default.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Feature: Terragrunt opentofu support</issue_title>
<issue_description>### Related to

Configuration, Other

Impact

nice to have

Missing Feature

It would be great if we could swap from terraform to opentofu in terragrunt. Currently this doesn't seem to be an option or isn't fully documented.

Implementation

If we could override the --tf-path=terraform param injected that would be great.

Design

No response</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Feature: Terragrunt opentofu support #3397

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