Set the order in which event nodes run across behaviors (#264)

Which of two events ran first depended on hidden lists: the order of
the behavior instances and the order in which nodes were created. A
graph had no way to say that one On update must run before another,
and an On update of one behavior could run before a key event of
another.

- A frame now runs event kind by event kind over all behaviors: On
  disable and On enable, key down, key up, key held, timer, collision
  enter, stay and exit, animation finished, click, mouse wheel and at
  last On update.
- All 17 event nodes have a field Order, a whole number, default 0,
  negative allowed. Within one kind a lower Order runs earlier, no
  matter which behavior holds the node.
- On a tie the current hierarchy decides from top to bottom, then the
  order in which the nodes were created. The old rule that a behavior
  enabled later goes to the end is gone.
- The node shows Order: 5 only when the value is not 0, so existing
  graphs look the same.
- The rule lives as pure functions in core/graph/eventOrder.ts. The
  interpreter can now fire a single event node.

Changes in existing projects:

- An object destroyed in a frame gets no further event in that frame.
  On disable and On destroy still come at the end of the frame.
- New instances get all their On start first, then all On enable.
  Teardown runs all On disable first, then all On destroy.
- State events follow right after the event kind that caused them.
- Four unit tests had fixed the old order and are adjusted:
  two in behavior-events, one in physics-system, one in key-repeat.

Tests:

- ./check.sh: 191 files, 2784 tests, CHECK EXIT 0.
- GM_STEPS=1-6: ALL PASSED, 280 checks.
- Full e2e run (local): ALL PASSED, 1551 checks, measured.
- tests/core/event-order.test.ts: 11 tests for the rule, the field on
  all 17 nodes, order across behaviors, key before update, two nodes
  in one graph, On start, hierarchy after late enable and reorder at
  runtime, state events, save and load.
- e2e 6z-viii, 2 checks with real mouse and keyboard: Order -1 set in
  the inspector shows on the node, and a run logs B, A although B is
  lower in the hierarchy.
- Counter-checks: 5 in unit tests and 1 in the browser, all fail as
  expected. The originals were restored and checked with cmp.

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, 1549 checks (GM_STEPS=20 for one step)
+node tools/seed-e2e.mjs && node tools/e2e.mjs      # the editor, 1551 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