[Skill Bug]: Optimize Foundry related scenarios by distributing its instructions to relevant skills

### Preflight Checklist

- [x] I have installed the [latest version of GitHub Copilot for Azure in VS Code](https://github.com/microsoft/GitHub-Copilot-for-Azure/releases/latest).
- [x] I have checked existing resources, including using the /help command in the chat window.
- [x] I have searched for [similar issues](https://github.com/microsoft/GitHub-Copilot-for-Azure/issues).

### Repro Steps

Some foundry integration test prompts have been consistently triggering other skills. Here are a few examples:

- prompt: Grant a user the Azure AI User role on my Foundry project. skill: azure-rbac
- prompt: How much quota do I need for a production Foundry deployment? skill: azure-quotas

I suggest we move/replicate the relevant instructions from microsoft-foundry skill into these skills that have been consistently triggered for its target scenarios so they can still provide value to the user.

Example test run logs:
https://agreeable-dune-0f718070f.1.azurestaticapps.net/nightly-runs.html?file=2026-05-19%2F26080086422%2Fmicrosoft-foundry%2Fmicrosoft-foundry_-_Integration_Tests_skill-invocation_invokes_microsoft-foundry_skill_for_RBAC_role_assignment_prompt%2Fagent-metadata-2026-05-19T06-27-18-943Z.md

https://agreeable-dune-0f718070f.1.azurestaticapps.net/nightly-runs.html?file=2026-05-13%2F25781581044%2Fmicrosoft-foundry%2Fmicrosoft-foundry_quota_-_Integration_Tests_Quota_Before_Deployment_suggests_capacity_calculation%2Fagent-metadata-2026-05-13T06-10-15-867Z.md

### Prompt

See repro steps.

### Expected Result

Regardless what skill is invoked, we want to give the agent useful instruction to help the user accomplish their goal.

### Actual Result

The triggered skill doesn't have foundry bespoke instructions, and thus they cannot provide value to the user.

### Attachments

_No response_

### Regression?

_No response_

### Additional Context

_No response_