Stream long sounds from an Opus copy instead of decoding them (#349)

A sound was decoded whole as soon as the project opened, in the editor
and in a released game: five minutes of stereo held some 115 MB for as
long as the page was open. A sound with Stream on now plays from a copy
as Opus in Ogg, fetched a piece at a time and decoded a few seconds
ahead by WebCodecs, so a game holds a few megabytes for it.

- The Stream switch is a row of the sound, off by default. The Sound
  tab suggests it from a minute on and says how far the copy has got.
- StreamKeeper makes the copies in the browser, a moment after the
  last change, one at a time: the sound's own and one per clip of its
  cut, fades and Reverse baked in. A copy that is no longer wanted is
  taken off and deleted once the project is saved without it.
- streamTable says which played names stream from which copy. A clip
  without a fitting copy, a Sample and a Reverb impulse stay decoded.
  A sound with Stream on is never decoded ahead.
- The page fetches by Range and takes the whole file from a server
  that ignores it, as the CI's PHP server does. It keeps the bytes
  and the first two seconds decoded, the rest goes four seconds ahead.
- A jump decodes 32 packets before the place first. Measured in
  Chrome, what follows is then the same to the bit as decoding from
  the start. With 4 packets it was 0.06 off.
- The stream-player on the FX worklet reads the samples at the rate
  of the context along a Catmull-Rom curve. What comes late is silent
  and skipped once it is there, so a clip keeps its beat.
- The opening stretch goes with the player as it is made. Sent by
  message it came a few milliseconds late, and 557 samples of the
  attack were lost.
- Pitch on a streamed sound is a shifter after the player, as on a
  bus: the length stays and it is heard 42.7 ms late.
- Bakes of patterns and songs (#340) always stream now.
- The song timeline draws a streamed sound from its copy decoded at
  8 kHz, keeping only the peaks.

Tests:
- Gate: CHECK EXIT 0, 280 files, 4312 tests (31 new: ogg +3,
  stream-queue 6, streams 11, streaming 6, sound-library +5).
- e2e 34: ALL PASSED, 106 checks (7 new). Five minutes of mono,
  4.8 MB as WAV, 3.6 MB as its copy: streamed the renderer grows by
  5.8 MB, decoded by 69.6 MB. Offline at 48 kHz, start, loop seam and
  a reversed clip are the copy decoded whole to the sample (0).
- Counter-checks red as they should be: no pre-roll, no catch-up of
  late samples at the end, no opening stretch, a streamed sound
  decoded ahead.

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, 1928 checks (GM_STEPS=20 for one step)
+node tools/seed-e2e.mjs && node tools/e2e.mjs      # the editor, 1935 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