fix: warn user when Antigravity MCP config is written globally

When the user selects project-level install, Antigravity's MCP config
still goes to ~/.gemini/antigravity/mcp_config.json since Antigravity
only supports global MCP configuration. Show a warning so this is not
surprising.

Author: borhenryk

install.ps1

@@ -1571,6 +1571,10 @@ function Write-McpConfigs {
                 Write-Ok "Gemini CLI MCP config"
             }
             "antigravity" {
+                if ($script:Scope -eq "project") {
+                    Write-Warn "Antigravity only supports global MCP configuration."
+                    Write-Msg "  Config written to ~/.gemini/antigravity/mcp_config.json"
+                }
                 Write-GeminiMcpJson (Join-Path $env:USERPROFILE ".gemini\antigravity\mcp_config.json")
                 Write-Ok "Antigravity MCP config"
             }

install.sh

@@ -1475,6 +1475,10 @@ write_mcp_configs() {
                 ok "Gemini CLI MCP config"
                 ;;
             antigravity)
+                if [ "$SCOPE" = "project" ]; then
+                    warn "Antigravity only supports global MCP configuration."
+                    msg "  Config written to ${B}~/.gemini/antigravity/mcp_config.json${N}"
+                fi
                 write_gemini_mcp_json "$HOME/.gemini/antigravity/mcp_config.json"
                 ok "Antigravity MCP config"
                 ;;