Improve tensioning: default motor movement, stall detection, gradual release

[fabricenoelbourquin]

Summary

• Move motors by default: tension.py now moves motors without needing --move-motors. Added --no-move-motors flag to skip. --move-motors kept for compatibility.
• Stall detection: Replaced fixed-duration movement loops with position-based stall detection — motors move until stalled, hold 1s, then proceed. No more unnecessary waiting at the edges.
• Gradual torque release: After preconditioning, torque ramps down over 1s before re-engaging at the relaxed position, preventing tendon snap-back.

Test plan

• uv run pytest tests/test_tension.py — all 4 tests pass
• Run tension.py on hardware and verify motors move by default
• Verify --no-move-motors skips motor movement
• Verify stall detection transitions smoothly between directions
• Verify gradual torque release prevents tendon snap-back

🤖 Generated with Claude Code

[clemens-chr]

Good frabrice