Let a text field select from right to left with the mouse (#236)

Dragging from right to left in a canvas text field only moved the
cursor. The hidden input behind the field got every selection sorted
and without a direction. Its selectionchange echo then handed back the
sorted range, and the anchor jumped to the mouse on the first move.

- KeyboardBridge sets the selection with 'backward' when the focus
  lies before the anchor, and reads selectionDirection when the input
  reports a change.
- TextField passes anchor and focus through unchanged. Its own
  sorting is gone.
- Shift+Left runs through the same path. The cursor should now sit at
  the moving end there too. This is not tested on its own.

Tests:
- ./check.sh: 167 files, 2435 tests, CHECK EXIT 0
- e2e 2: ALL PASSED, 25 checks. New check 2d-ii drags right to left
  in the name field and reads start 0, end 13, direction backward.
- Counter-check without the direction: 2d-ii fails with end 2, the
  reported symptom.
- e2e check total in README goes to 1401 (computed, not run in full).

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

README.md

@@ -43,7 +43,7 @@ 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, 1400 checks (GM_STEPS=20 for one step)
+node tools/seed-e2e.mjs && node tools/e2e.mjs      # the editor, 1401 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