[Module Proposal]: `avm-res-app-agent`

### Check for previous/existing GitHub issues/module proposals

- [x] I have checked for previous/existing GitHub issues/module proposals.

### Check this module doesn't already exist in the module indexes

- [x] I have checked for that this module doesn't already exist in the module indexes.

### Bicep or Terraform?

Terraform

### Module Classification?

Resource Module

### Module Name

avm-res-app-agent

### Module Details

Terraform AVM resource module for Azure SRE Agent. Aligns with Bicep #2582

Initial implementation based on latest spec requirements, passes lint rules:

https://github.com/kewalaka/terraform-azure-avm-res-app-agent/

This resource is currently in preview (2026-01-01-preview). Implementation uses the azapi provider (~> 2.7) with schema_validation_enabled = false as required API versions are not yet in the embedded schema.

### Do you want to be the owner of this module?

No

### Module Owner's GitHub Username (handle)

_No response_

### (Optional) Secondary Module Owner's GitHub Username (handle)

_No response_

Start by reviewing the linked terraform-azure-avm-res-app-agent implementation and the latest Azure SRE Agent specification. Check how the module uses the azapi provider with schema validation disabled and verify it meets Terraform AVM standards and lint rules; done means the module is ready for inclusion in the module indexes.

Written by the indexing model from the issue text.