Silence a free video once its sprite is destroyed (#420)

A sprite whose Video clock is free played its video on after it was
destroyed, heard in a game, until the player was let go 2 to 4 s
later. A driven one was already held and quiet after 100 ms.

- The library holds and quiets a free player nothing asked for in
  HUSH_MS, as it did a driven one. That covers Destroy, a scene load,
  the end of a run and a sprite switched off.
- Asked for again before it is let go, it plays on from where it was
  held, heard only in a run. A hidden page leaves it alone, as the
  sweep does.
- A sprite only out of view keeps its free video playing and heard.
  Whether a video is heard should not hang on the camera. Before, it
  ran 2 to 4 s and was then let go. Now it plays on, which opens its
  player even where it was never in view.

Tests:
- Unit: video-library 1 new. A free player losing its wearer is held
  and quiet 200 ms later, stays so through a new run, plays on heard
  when asked again with the same element, and runs on on a hidden
  page.
- e2e 66 on melektaus-atx: ALL PASSED, 36 checks, 66g-ii new. Heard
  31 frames before Destroy, held and muted in every frame read after.
- Counter-probe without hushing free players: the unit test and only
  66g-ii fail, the player plays on heard (paused false, muted false).
- Gate on melektaus-atx: 309 files, 4797 tests.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

README.md

@@ -47,7 +47,7 @@ npm run build        # writes dist/ and regenerates index.html; the folder is wh
 The browser suite and the three example games need a machine with a GPU:
 
 ```bash
-node tools/seed-e2e.mjs && node tools/e2e.mjs      # the editor, 2073 checks (GM_STEPS=20 for one step)
+node tools/seed-e2e.mjs && node tools/e2e.mjs      # the editor, 2074 checks (GM_STEPS=20 for one step)
                                                    #   every tool signs in first – see the Accounts page
 node tools/seed-jumprun.mjs && node tools/smoke-jumprun.mjs
 node tools/seed-tetris.mjs && node tools/smoke-tetris.mjs