Add support for arrangment_clip warp_markers

[PhotonicVelocity]

Description

Extends the arrangement‑clip namespace (from PR-180) to include warp‑marker and warp‑mode helpers (added in PR-177 and PR-178) so arrangement clips can be inspected and edited in the same way as session clips when the warp‑marker API is available.

Adds:

• /live/arrangement_clip/get/warp_markers
• /live/arrangement_clip/add_warp_marker
• /live/arrangement_clip/move_warp_marker
• /live/arrangement_clip/remove_warp_marker
• /live/arrangement_clip/get/available_warp_modes

Checklist

• The title is descriptive and summarises the new changes
• The code and any comments are consistent with the current code style
• For any new or modified API endpoints, I have added appropriate documentation to README.md
• For any new or modified API endpoints, I have added unit tests covering the new functionality
• I have verified that all unit tests pass (see CONTRIBUTING.md for guidance)

[ideoforms]

Hi @PhotonicVelocity, thanks for all of the PRs! I'm away on an artistic residency so can't take a look at them right now, but will review them all when I'm back in a couple of weeks.

[PhotonicVelocity]

@ideoforms no worries, glad to help!