Description:
Under the no host installed scenario (neither copilot nor claude on PATH), running azd tool install azure-skills shows two issues on macOS and Linux.

• MacOs: If the user is prompted to install Copilot CLI and answers n, the final error is: copilot: Azure Skills was installed via copilot but verification failed. This is inconsistent with the actual user action (declined installation). It should return a clear error stating "Host not installed; cannot proceed with Azure Skills installation," rather than indicating "Installed but verification failed."

• Linux VM: After running azd tool install azure-skills, if the user enters y when prompted to install Copilot CLI, the flow gets stuck at the PATH/profile confirmation step (no response for a long time and no further input is accepted).

The expected behavior should match Windows: fail with a clear message that no supported host (e.g., Copilot or Claude) was detected, and provide clear installation guidance.

Steps to Reproduce:

1. copilot and claude not on PATH
2. Run azd tool install azure-skills.

Environment:

• Azd version: azd version 1.26.0-beta.1-pr.6468449 (commit f510f40) (stable).
• OS: Linux, MacOS.

Expected Behavior:
When no host is installed, azd tool install azure-skills should consistently fail or prompt the user to install a host.

@hemarina and @RickWinter for notification.