Add authentic plane gameplay reels to landing page

[RRG314]

Summary

• add clean barrel-roll and vertical-loop recordings captured from the deployed World Explorer build
• add responsive gameplay video cards with native controls and accessible labels
• prevent MP4 downloads during initial landing load with poster-only preload behavior
• serve MP4/WebM with correct MIME types in the local preview server

Verification

• source verification passed (535 modules / 540 targets)
• clean hosting artifact build and integrity verification passed
• strict hosting reachability passed (563/563 files)
• strict asset reachability passed (97 tracked assets, zero unreachable)
• desktop and 390x844 Playwright layout checks passed
• both 1280x720 H.264 clips loaded and played through native controls
• landing browser console: zero errors and warnings
• in-game Baltimore regression: 25,449 buildings, 14,188 roads, 49/49 terrain tiles