Phone portrait shows every joint slider at once in a collapsible tray under the model, in place of the one-joint lever #276

From #50 (owner: "i dont want only one at a time. i preferred the old ui") and replaces #92's drive sheet.

Done:

• [ ] In phone portrait, #touch (one joint at a time) is gone. All joints plus the gripper are compact rows (label, slider, value), each with an intent mark and an actual mark.
• [ ] The rows sit in a tray under the model that collapses to one line and opens with a tap. STOP stays visible either way.
• [ ] A test at 390x844: all joint sliders are present at once, and the tray collapses and opens.
• [ ] forge.json untouched. bun --cwd Software/so101 test passes.

Files: Software/so101/src/viewer.html, src/ui/drive.js, src/ui/mobile.css.