Linux PowerShell 7.6 Preview Function App fails to load "Functions" node with ServiceUnavailable error

[v-ruizh]

OS: Win 11 x64
Build Version: 20260513.1
Regression: Not a Regression

Repro Steps:

1. Create a Linux PowerShell function app using "PowerShell 7.6 (Preview)" runtime.
2. Expand the above function app -> Expand the "Functions" node.
3. Check whether the Functions node loads successfully.

Expect:
The "Functions" node loads successfully. No error is shown

Actual:
An error shows in the "Functions" node.

More Info:
This issue does not reproduce for Windows PowerShell function app created using "PowerShell 7.6 (Preview)" runtime.