Draw the editor's mouse pointer from SVG files, on screen too

The pointer drawn into an editor recording lived as paths in code, so
it could not be looked at or edited by hand. The shapes are now SVG
files, and the editor can show the same pointer on screen, so what is
recorded is what was seen.

- src/core/recording/cursors/ holds one file per shape: arrow, hand,
  open-hand, fist, move, crosshair, text and resize. Resize is turned
  for the vertical and diagonal directions.
- data-hot="x y" on the <svg> is the hotspot in viewBox units. Width
  and height in the file are ignored, and anything before <svg>, such
  as <?xml ...> from a drawing program, is cut off.
- The open hand had six fingers. It has a thumb and four now, the
  middle one longest.
- CURSOR_SIZE = 0.8 scales every pointer the same on screen and in a
  recording, so the files keep their units.
- General settings has "Custom mouse pointer", on by default. It hangs
  the files into Pixi's cursorStyles as CSS cursors with the keyword as
  fallback, so the system still draws the pointer and the canvas does
  not. Off gives Pixi's own values back at once.
- A recording draws the pointer from the same files at its own size,
  so it stays sharp in 4K. It still reads the shape from the canvas
  when that holds a url(...) cursor.

Tests:
- Unit recording and view-tween: 3 new, green. They read viewBox and
  data-hot in an edited form, the boxes of turned shapes, the default
  size and old settings without the switch. Red without data-hot and
  without cutting before <svg>.
- e2e 46i-ii: the canvas cursor is a url(...) ending in default and
  the image loads. Off gives inherit and stores false, on brings the
  file back. Red without useCursorFiles.
- e2e 67e: the recording is still black at the mouse position.
- The README names 2046 e2e checks.
- Gate on melektaus-atx: 304 files, 4702 tests green.

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, 2045 checks (GM_STEPS=20 for one step)
+node tools/seed-e2e.mjs && node tools/e2e.mjs      # the editor, 2046 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