Add recorded demos

[fracapuano]

This PR allows to record and execute demos with very compact instructions, such as:

from orca_core import OrcaHand

hand = OrcaHand()

success, message = hand.connect()
print(f"connect() -> success={success}, message={message}")
if not success:
    raise RuntimeError(message)

# Enables torque, sets control mode/current, and computes wrap offsets.
hand.init_joints(move_to_neutral=True)

hand.run_demo("main", cycles=3)

In theory this should also zero-day support the sim backend. Effectively, here we demo presets directly in orca_core, unifying backends under a shared hand.run_demo(...) command. It also mildly touches scripts/, as the hard coded presents there recorded are now stored within a demo_presets.py file.