Fix Linux daemon install checks when systemd user bus env is missing (#34884)

* daemon(systemd): fall back to machine user scope when user bus is missing

* test(systemd): cover machine scope fallback for user-bus errors

* test(systemd): reset execFile mock state across cases

* test(systemd): make machine-user fallback assertion portable

* fix(daemon): keep root sudo path on direct user scope

* test(systemd): cover sudo root user-scope behavior

* ci: use resolvable bun version in setup-node-env

.github/actions/setup-node-env/action.yml

@@ -61,7 +61,7 @@ runs:
       if: inputs.install-bun == 'true'
       uses: oven-sh/setup-bun@v2
       with:
-        bun-version: "1.3.9+cf6cdbbba"
+        bun-version: "1.3.9"
 
     - name: Runtime versions
       shell: bash