Consolidate asset 'movies/' dirs into 'videos/' for consistency

[jonfroehlich]

Consolidate asset video dirs: standardize on videos/ (drop movies/)

Module asset folders are inconsistent — some use assets/movies/, others assets/videos/, and arduino/ and esp32/ have BOTH:

• movies/: arduino, esp32, sensors, signals (+ signals notebook subdirs)
• videos/: advancedio, arduino, assets (root), communication, cpx, electronics, esp32

Proposal: standardize on videos/ — the top-level assets/videos/ already uses it, and "videos" is the clearer, more conventional name. (Agreed with Jon, 2026-06-23.)

Scope

• git mv each <module>/assets/movies/* into <module>/assets/videos/ (merging where both exist in arduino/esp32).
• Update all references in source .md (search assets/movies/).
• Remove the now-empty movies/ dirs.

Notes

• Coordinate with the GIF→MP4 conversion (companion issue) — both touch these folders; do the rename first, then convert, to avoid double-churn.
• The html-proofer link-check gate will catch any reference missed by the move (it just caught 4 stale /assets/movies/ refs during the Jekyll 4 upgrade).
• signals/ is migrating to makeabilitylab/signals (Signals Lessons #116) — skip its dirs here.

Part of V2.0.