Add carry_object_to_target task to starter_pack

[build4mbottom]

Create a new task under starter_pack that requires:

• grasping an object
• walking to a target
• placing the object at target pose

Re-use existing primitives.

Label: good-first-issue

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Acceptance Criteria

• Task folder created under:
  src/hts_tasks/packs/starter_pack/carry_object_to_target/
• task.yaml defines:
  • success condition (object at target pose)
  • reward shaping for grasp + locomotion + placement
• Task loads via automatic discovery
• hts train runs without error
• Basic smoke test passes