Defer video/pose frame-count check off project load (KLAUS-505)

[gbeane]

Summary

Removes the up-front video/pose frame-count validation from project load. Today every video file is opened via cv2.VideoCapture at load to compare its frame count against the pose file — the dominant, cache-resistant load cost on large projects.

Measured on a 488-video project (external SSD): the video reads were ~24.5s of the load scan (91%), and even a fully warm parallel load went 0.11s → 1.84s solely because of this check.

What changed

• enable_video_check now defaults to False; when True it performs the (now opt-in) up-front sweep.
• The check is deferred to when a video is actually opened: CentralWidget.load_video shows a non-blocking warning (MessageDialog) on a video/pose frame mismatch, at zero extra I/O (the pose and player are already open).
• Feature-extraction workers log a warning on mismatch for headless/batch runs.
• New get_fps_and_nframes reads fps + frame count from a single video open.

Rationale

The training / feature / prediction pipeline is pose-driven — features come from the pose file and labels are indexed to pose frames. A video/pose frame mismatch does not corrupt features or predictions; it only affects frame-display alignment in the labeling GUI. So the correct home for the check is video-open time, not project load.

Tests

Full suite green. New/updated coverage: the deferred default performs no video opens, the opt-in path (enable_video_check=True) still raises on an unreadable video, the worker logs on mismatch, and the GUI mismatch message helper.

Jira: KLAUS-505

[Copilot]

Pull request overview

This PR reduces expensive project-load latency by making the video/pose frame-count validation opt-in at load time and deferring mismatch reporting to (a) GUI video-open time and (b) headless feature-extraction workers, while adding a single-open helper to fetch FPS + frame count.

Changes:

• Default enable_video_check to False in Project/VideoManager, making the up-front sweep opt-in.
• Add deferred mismatch reporting: GUI warning on CentralWidget.load_video() and worker-side logging in parallel_workers.
• Introduce get_fps_and_nframes() to read FPS and frame count from one cv2.VideoCapture open; update tests accordingly.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tests/ui/test_central_widget.py	Adds unit tests for the GUI mismatch message helper.
tests/project/test_project.py	Updates project-load tests to reflect deferred-by-default behavior and opt-in failure behavior.
tests/project/test_parallel_workers.py	Updates worker tests to use get_fps_and_nframes and adds logging coverage for mismatch warnings.
src/jabs/video_reader/utilities.py	Adds get_fps_and_nframes() to fetch FPS + frame count from a single video open.
src/jabs/ui/main_window/central_widget.py	Adds mismatch message builder and triggers a GUI warning on deferred mismatch detection during video open.
src/jabs/project/video_manager.py	Changes enable_video_check default to False and updates docstrings accordingly.
src/jabs/project/project.py	Changes enable_video_check default to False and clarifies deferred validation behavior in docs.
src/jabs/project/parallel_workers.py	Uses get_fps_and_nframes() and logs warnings on video/pose frame-count mismatches for headless runs.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.