Loop over a list and stop at the first match with For each (#249)

Finding the first item that matches took Count, Repeat, Item at and a
Branch, and the loop could not stop once it had found something. A graph
has no lambdas, so the predicate is an input that is read every round.

- For each runs body once per element, with item and index set, and
  goes on at done.
- Its break input is read anew before every round, after item is set.
  Once it is true the loop ends there and that round's body does not
  run.
- done sees the matching item and index with stopped true. Without a
  match it sees no item, index -1 and stopped false, the OrDefault.
- RepeatResult has optional items, stopWhen, stopped and exhausted.
  GraphInterpreter.loop reads them, Repeat runs as before.

Tests:
- ./check.sh: 180 files, 2623 tests, CHECK EXIT 0
- e2e GM_STEPS=1-6: ALL PASSED, 269 checks
- 5 interpreter tests in graph.test.ts, 2 catalog cases
- e2e 6z-iv: the palette creates the node, and a search for
  Name == "Gold" in Axe, Gold, Bow, Gold logs "1true"
- Counter-checks: without the break check 2 unit tests fail, and with
  break not read over its edge 6z-iv fails
- This commit alone: tsc and the three touched unit files pass
  (349 tests)

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, 1477 checks (GM_STEPS=20 for one step)
+node tools/seed-e2e.mjs && node tools/e2e.mjs      # the editor, 1479 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