Add record/training pause-resume and dataset edit/merging/rerecord/re…

[albertozafra7]

Summary

This PR improves LeLab recording and training workflows with the following features:

1. Add/Re-record specific demonstrations in existing datasets
2. Replay specific episodes from dataset videos
3. Pause/Resume recording from the UI
4. Pause/Resume local training jobs from the UI
5. Fix episode listing bug ("No episodes found") for HF dataset metadata

Main changes

Dataset editing (specific demonstrations)

• Added dataset episode listing endpoint: GET /dataset-episodes
• Added in-place episode deletion flow before re-recording selected episodes
• Added a dedicated frontend page for the Add/Re-record workflow:
  • Dataset selection
  • Episode selection
  • Delete selected episodes
  • Start recording to append/recreate demonstrations

UI screenshots

• Main dataset edit entry point
  

• Dataset editing views
  
  

Episode replay

• Added endpoint to fetch per-episode video segment metadata:
  • file_path
  • from_timestamp
  • to_timestamp
• Added secure video file serving endpoint for replay
• Added replay modal in frontend with per-camera video playback for selected episodes

UI screenshots

• Episode re-recording
  

• Episode replay
  

Pause/Resume recording

• Added recording pause state and pause/resume handlers
• Added endpoints:
  • POST /pause-recording
  • POST /resume-recording
• Added frontend Pause/Resume controls and paused-state handling

Pause/Resume training (local jobs)

• Added paused job state
• Added pause/resume operations for local jobs using SIGSTOP / SIGCONT
• Added endpoints:
  • POST /jobs/{job_id}/pause
  • POST /jobs/{job_id}/resume
• Added frontend Pause/Resume controls and state-aware polling for training jobs

UI screenshot

Files changed

• lelab/record.py
• lelab/server.py
• lelab/dataset_edit.py
• lelab/jobs.py
• frontend/src/pages/Recording.tsx
• frontend/src/pages/RerecordEpisode.tsx (new)
• frontend/src/pages/Landing.tsx
• frontend/src/App.tsx
• frontend/src/pages/Training.tsx
• frontend/src/lib/jobsApi.ts

Notes

• Training pause/resume currently applies to the local runner.
• This PR is focused on LeLab UX and dataset edition workflow.

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