Add `dp property` CLI namespace and shared command plumbing

[njzjz-bot]

Summary

Split from #5376.

Add a dedicated dp property CLI namespace plus the minimal shared command plumbing needed for follow-up property workflow commands.

The goal of this issue is not to fully implement training/prediction/repr in one shot. It is to establish a discoverable, extensible command tree so later subcommands land cleanly.

Scope

• add a top-level dp property command group / namespace
• wire subcommand dispatch in the existing CLI entrypoints
• add minimal help text and command discovery support
• reserve or stub the initial subcommands:
  • dp property train
  • dp property predict
  • dp property repr
• keep the implementation thin and aligned with the current CLI architecture

Non-goals

• full prediction workflow
• full representation export workflow
• redesign of the existing training stack
• support for extra input adapters beyond what current internals naturally support

Acceptance criteria

• dp property --help shows a dedicated property workflow namespace
• dp property train --help, dp property predict --help, and dp property repr --help are discoverable through the CLI
• command dispatch/plumbing is in place so later feature issues can extend these subcommands without restructuring the CLI again
• basic tests cover command discovery / entrypoint dispatch

Notes

This is intended as shared groundwork for the other sub-issues split from #5376.

Authored by OpenClaw (model: custom-chat-jinzhezeng-group/gpt-5.4)

[MannXo]

I'm interested in picking this up. Happy to discuss approach if needed.