fix: prioritize SST's Pulumi over system-installed versions (#6316)

Prepend SST's bin directory to PATH when spawning Pulumi processes.
This ensures SST uses its bundled Pulumi binaries instead of
system-installed versions, fixing compatibility issues with
Pulumi v3.214.0+ which removed the -root flag from pulumi-language-nodejs.

Fixes deployment failures on GitHub Actions ubuntu-latest runners
where a newer Pulumi is pre-installed.

Author: smorimoto

pkg/project/run.go

@@ -249,6 +249,13 @@ func (p *Project) RunNext(ctx context.Context, input *StackInput) error {
 	}
 
 	env := os.Environ()
+	// Prepend SST's bin directory to PATH to ensure SST's Pulumi is used over system-installed versions
+	for i, e := range env {
+		if strings.HasPrefix(e, "PATH=") {
+			env[i] = "PATH=" + global.BinPath() + string(os.PathListSeparator) + strings.TrimPrefix(e, "PATH=")
+			break
+		}
+	}
 	for key, value := range p.Env() {
 		env = append(env, fmt.Sprintf("%v=%v", key, value))
 	}