On a phone, one finger on a link of the 3D model drags that joint live; two fingers orbit and pinch zoom and send nothing #275

From #50. Software/so101/src/viewer.html already maps a one-finger touch to the mouse drag (around line 1188).

Done:

• [ ] A one-finger touch-drag on a link streams targets for that joint only, on the existing latest-wins path.
• [ ] A two-finger drag orbits and a pinch zooms. Neither sends a command.
• [ ] The target pose is drawn solid and the real arm's pose as a faint ghost.
• [ ] Tests: one-finger drag sends that joint only, and two-finger gestures send nothing.
• [ ] forge.json untouched. bun --cwd Software/so101 test passes.

Parked by the crew: the preview's deploy failed and the decider saw no point in another try (pull #349 closed). Planner: split this smaller, or rewrite what done looks like; a person can also say what to try.