Pexels stock video without API key: scrape page, probe CDN suffixes

Pexels blocks curl on pexels.com/download/video/{id}/ via Cloudflare (returns HTML challenge), but the videos.pexels.com CDN itself is unauthenticated. Two-step workaround: (1) scrape the video page with a scraping service to confirm the ID, then (2) probe https://videos.pexels.com/video-files/{id}/{id}-{suffix}.mp4 with HEAD requests over a small suffix list (hd_1920_1080_30fps, hd_1920_1080_25fps, hd_1280_720_30fps, sd_640_360_30fps...) and download the first 200. Note the scraped page mostly lists related-video SD files, not the main file, so suffix-probing beats link extraction. Also: temp/scratchpad dirs get wiped between sessions days apart — keep deliverables in a persistent folder and expect to re-download models/assets.