Add GOOGLE_GENAI_USE_VERTEXAI to setup script manual instructions

[Copilot]

The setup script automatically sets GOOGLE_GENAI_USE_VERTEXAI when gh CLI is available but omits it from manual setup instructions, leaving users without gh CLI unable to configure Vertex AI.

Changes

• Automatic setup: Added GOOGLE_GENAI_USE_VERTEXAI to gh variable set commands (line 458)
• Manual setup: Added variable documentation to else block with usage note (lines 477-480)

# When gh CLI is available
gh variable set GOOGLE_GENAI_USE_VERTEXAI --body "true" --repo "${GITHUB_REPO}"

# When gh CLI is not available (manual instructions)
echo "🤖 Variable Name: GOOGLE_GENAI_USE_VERTEXAI"
echo "   Variable Value: true"
echo "   (Set to 'true' to use Vertex AI, or use GOOGLE_GENAI_USE_GCA for Code Assist)"

This establishes parity between both setup paths and documents the alternative GOOGLE_GENAI_USE_GCA variable for Code Assist users.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Improve code to cover full if/else branches</issue_title>
<issue_description>apply changes based on this feedback

The new GOOGLE_GENAI_USE_VERTEXAI variable is set automatically when gh CLI is available, but it's not included in the manual setup instructions in the else block (lines 462-477). Users without the gh CLI won't know to set this variable manually. Consider adding documentation for this variable in the else block, similar to the other variables.

</issue_description>

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

• Fixes Improve code to cover full if/else branches #1

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.

[huan]

LGTM

[Copilot]

Pull Request Overview

This PR adds the GOOGLE_GENAI_USE_VERTEXAI variable to both automatic and manual setup paths in the workload identity setup script, ensuring users without the gh CLI can properly configure Vertex AI.

Key Changes:

• Added automatic setting of GOOGLE_GENAI_USE_VERTEXAI when gh CLI is available
• Added manual instructions for GOOGLE_GENAI_USE_VERTEXAI with explanatory note about the alternative GOOGLE_GENAI_USE_GCA variable

---

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

[Copilot]

The parenthetical note mentions using GOOGLE_GENAI_USE_GCA but doesn't provide guidance on which variable to set or if both can be set simultaneously. Consider clarifying that these are mutually exclusive options, or explain that users should choose one based on their needs. For example: "(Set to 'true' to use Vertex AI. Alternatively, use GOOGLE_GENAI_USE_GCA='true' for Code Assist instead)"

Suggested change

	echo " (Set to 'true' to use Vertex AI, or use GOOGLE_GENAI_USE_GCA for Code Assist)"
	echo " (Set to 'true' to use Vertex AI. Alternatively, set GOOGLE_GENAI_USE_GCA='true' for Code Assist. These options are mutually exclusive; set only one based on your needs.)"