Pre-planning cup grabbing

[Yao Chen (yao-stuy)]

Dynamic cup/glass pickup used to discover unreachable candidates by physically
reaching for them — approach, find the grab descent unplannable, retreat — wasting
a full reach-and-back-out per bad candidate.

tryGrab now plans both the approach and grab descent up front without moving. An
unreachable candidate is skipped with the arm still parked at the observe pose;
only a candidate whose legs both plan is grabbed, and the validated plans are
executed directly instead of re-planned.

The grab sequence is otherwise unchanged (approach → open → descend → verify →
attach → retreat), and grabAndVerifyHolding remains the backstop that a cup was
actually picked up. Implemented by splitting moveToRawPose into planRawPose +
executePlan; existing callers are unaffected.

🤖 Generated with Claude Code

[Nicolas Palpacuer (NickPPC)]

Can you clean up the comments a little? claude added a lot of comments.