refactor(players): delete dead VideoPlayer that restarted a unit that does not exist (869f8v8yv)

[ibiltari]

Fixes ClickUp 869f8v8yv.

Problem

VideoPlayer (players/VideoPlayer.py) was dead code. Nothing instantiated it, and its own docstring said not to use it. It was also broken: run() restarted videocomposer.service, and that unit does not exist (the real one is cuems-videocomposer.service).

Why delete it instead of fixing the unit name

With a correct name, the engine would gain a working way to restart the videocomposer. That restart cuts the video on screen and leaves the engine holding layers the fresh videocomposer no longer has (869f8jn34), which breaks the "never auto-stop a running project" rule.

Changes

• Delete the VideoPlayer class and its export from players/__init__.py. VideoClient and VideoOutput stay.
• Delete CueHandler._video_players and CueHandler._front_video_player. They were set in __new__ and never read. NodeEngine.set_video_players is unrelated and unchanged.
• Remove their initialisation from the handler stub in tests/test_action_cue.py.
• In tests/testdev_engines_communication.py, which pytest does not collect, remove the "VideoPlayer was called" assertion. It was already false, because nothing created a VideoPlayer.

Testing

On test2, the engine suite was run on rc_1 (956a0f3) and on this branch, from separate checkouts, alternating:

• rc_1: 818 passed, 3 of 3 runs;
• this branch: 818 passed, 2 of 2 later runs.

This branch's first run died silently inside test_project_go.py. The cause is unrelated to this change: a wiring race between libmtcmaster and cuems-midiconnector, reproduced at 67/3011 with the connector running and 0/2744 with it stopped. It is tracked as ClickUp 869f8xepw.

Also on test2: the package imports, and the class and both attributes are gone.