Record the battle items commit in the session handoff

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

docs/SESSION_HANDOFF.md

@@ -605,4 +605,5 @@ the original.
 Checks: 337 unit tests with the local ROM (131 passed, 206 skipped
 without it); 97 Chromium/WebKit browser tests passed, 19 skipped
 intentionally; native and reference builds; reference, release and
-vendor checks; `git diff --check`. Not committed.
+vendor checks; `git diff --check`. Committed and pushed to `main` as
+`b13e09e`.