Add early disclaimer for unsupported subscription types

[Copilot]

Users with sponsored Azure subscriptions (and other unsupported types) encounter "No data found" errors without understanding why. The existing compatibility note is buried in the Usage section.

Changes

• Added prominent warning banner below the tool description linking to the existing compatibility check instructions
• Uses bold text and warning emoji for immediate visibility before installation

The disclaimer appears immediately after the introduction, directing users to verify subscription compatibility before attempting to use the tool.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Add disclaimer: not working for sponsored Azure subscriptions</issue_title>
<issue_description>Hi there...

This is not real an issue but more a heads-up. And maybe this is obvious for a lot of Azure power-users but it wasn't for me:
We have an Azure sponsored subscription from our Microsoft Partner membership.
To see the running costs of our Azure subscription we have to use the website "Microsoft Azure Sponsorships", the costs are not displayed in Azure Billing dashboard.

Therefore: this tool does not work with our subscription. It just lists "No data found".
I'd suggest to maybe include a disclaimer in the README on the frontpage of this GitHub page.

That's all. Have a great day.</issue_description>

<agent_instructions>Edit the repo README.md file so it is more explicit that not all the subscriptions are accessible with this tool. Just a short message below the title and first paragraph, with a link to the message in the readme on how to check it. </agent_instructions>

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

@mivano Unfortunately some of the subscription types do not work with the API calls. It is mentioned here: https://github.com/mivano/azure-cost-cli?tab=readme-ov-file#usage

You are right, it is not that obvious, so I will make this more explicit. Thanks for mentioning. </comment_new>

• Fixes Add disclaimer: not working for sponsored Azure subscriptions #278

---

💬 We'd love your input! Share your thoughts on Copilot coding agent in our 2 minute survey.

[Copilot]

Pull request overview

This PR adds a prominent disclaimer at the top of the README to inform users that not all Azure subscription types are compatible with the Azure Cost Management API used by this tool. This addresses issue #278 where users with sponsored Azure subscriptions were confused about why the tool wasn't working.

• Added a warning disclaimer below the main description explaining API limitations
• Linked the disclaimer to the existing detailed compatibility note in the Usage section
• Improved user experience by making subscription compatibility issues more visible upfront

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.