DOC: Disable video autoplay

[Roman Lutz (romanlutz)]

Description

Keep the Scanner and CoPyRIT walkthroughs embedded on the landing page, but require an explicit click on Play. The existing MP4 iframe URLs create browser-managed media documents that can autoplay both videos, including the video in the hidden tab.

• Point the iframes at local HTML players with native controls, poster images, playsinline, and preload="none", without an autoplay attribute.
• Pause hidden videos when switching tabs, and pause sibling players when another video starts. Restore tab observation after browser history navigation.
• Publish the players, existing videos, and posters using MyST's static_files configuration. Preserve the direct-video links and static-export placeholders.
• Keep the documentation version picker out of embedded player pages so it does not cover the video controls.

Related landing-page change: #2634. No PyRIT API or runtime behavior changes.

Tests and Documentation

Added regression tests for manual-playback defaults, published assets, sibling playback coordination, hidden-tab pausing, browser history restoration, and the version-picker opt-out. Updated the landing page and documented the static asset configuration and opt-out marker alongside their implementation.

Validation on the final code:

• uv run --frozen --no-sync pytest -q tests\unit\build_scripts\test_landing_video_players.py tests\unit\build_scripts\test_inject_version_picker.py: passed, 18 tests.
• uv run --frozen --no-sync ruff check build_scripts\inject_version_picker.py tests\unit\build_scripts\test_landing_video_players.py tests\unit\build_scripts\test_inject_version_picker.py: passed.
• uv run --frozen --no-sync ruff format --check build_scripts\inject_version_picker.py tests\unit\build_scripts\test_landing_video_players.py tests\unit\build_scripts\test_inject_version_picker.py: passed.
• node --check doc\assets\videos\player.js: passed.
• From doc, uv run --frozen --no-sync jupyter-book build --html --ci: passed.
• Automated headless Edge 154 at 1440×1000 and 390×844: passed. Both players remain paused at 0:00 with no MP4 requests before clicking Play; both native controls start playback; switching tabs pauses the hidden video; returning to a tab does not resume playback automatically. Embedded players have no version-picker overlays.

The original issue was reproduced on the published /latest/ landing page in automated headless Edge. Chrome and Firefox were not tested directly. The full unit suite and live-target integration tests were not run.

JupyText was not run because no notebook or paired Python documentation files changed.