compose: azd add does not force alpha schema annotation

[JeffreyCA]

• Make sure you've installed the latest version using instructions in the wiki

Output from azd version
azd version 1.11.0 (commit 5b92e06)

Describe the bug

To Reproduce

1. azd config set alpha.compose on
2. git clone https://github.com/luabud/TheCatSaidNo.git
3. cd TheCatSaidNo
4. azd init - select Use code in the current directory and then Confirm and continue initializing my app
5. Open azure.yaml in VS Code. Make sure the YAML extension is installed.

Expected behavior
There shouldn't be a schema validation error flagged - it may be due to line 1 referencing the 1.0 YAML schema instead of the alpha one:

# yaml-language-server: $schema=https://raw.githubusercontent.com/Azure/azure-dev/main/schemas/v1.0/azure.yaml.json

If you instead go through the azd init flow using the Create a minimal project flow, the generated azure.yaml uses the alpha schema:

# yaml-language-server: $schema=https://raw.githubusercontent.com/Azure/azure-dev/main/schemas/alpha/azure.yaml.json

Environment

• IDE and version: VS Code 1.95.3

[weikanglim]

We could make a small tweak to automatic update the resource schema annotation to alpha when running azd add, somewhere in the code here.

Just for completeness, the intellisense will show up as red, but azd will work as normal regardless of the schema annotation, so this is a minor presentation change but a good UX improvement.