docs: spec design tab "Pose 3D" (editor visuale + jog dei polsi)

Specifica per nuova tab GUI con viewport Three.js, gizmo
translate/rotate sui polsi DX e SX, modalita' Editor (preview) /
Jog (auto-move al mouseup), safety guard sui movimenti grandi,
checkbox precise toggle, save/load named poses in config.yaml.

Brainstorming nella sessione 2026-05-21.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitignore

@@ -6,6 +6,9 @@
 # Calibration data (per-installation, ricostruibile)
 data/
 
+# Brainstorming session files (visual companion)
+.superpowers/
+
 # Python
 __pycache__/
 *.py[cod]