docs(kit): re-pin to core 1.21.0 and teach report targets

ci/core-ref.json moves from 7bd93b8 (1.20.0) to f13b8fe (1.21.0,
website#233, report, block and hide). Chapter 2 gains a section on
registerReportTargets, registerGameIdentities and ctx.safety, and its call
count becomes twenty-three. template/module.json's coreApi becomes ^1.21.0
for the equality check; the template declares none of the new members.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E14m6SuuY6i1vASFeGDBeY

ci/core-ref.json

@@ -1,10 +1,20 @@
 {
   "repo": "https://gitea.whitlocktech.com/RunicGateway/website.git",
   "branch": "main",
-  "ref": "7bd93b8bb0da734a642587f256d10c523ca39bea",
+  "ref": "f13b8fe1fec9dc330a985430b8bd4f67c9ec26c5",
   "why": [
     "The core this kit is written against, pinned to a commit rather than a branch.",
     "",
+    "2026-10-30: moved from 7bd93b8 (1.20.0) to f13b8fe (1.21.0, website#233,",
+    "report, block and hide, USER_SAFETY.md). Chapter 2 was read again:",
+    "- 1.21.0: api.registerReportTargets, api.registerGameIdentities and",
+    "  ctx.safety.forViewer / staffAmong (chapter 2 gains a section, and its call",
+    "  count becomes twenty-three).",
+    "website#233 is the only core change in the window. The template declares",
+    "none of the new members, so nothing it does changed meaning; module.json's",
+    "coreApi becomes ^1.21.0 for the equality check. The real core run was",
+    "repeated at this ref, with the template as the only module in the directory.",
+    "",
     "2026-10-30: moved from 69998ec (1.19.0) to 7bd93b8 (1.20.0, website#232,",
     "account deletion, ACCOUNT_DELETION.md). Chapter 2 was read again:",
     "- 1.20.0: api.onUserDeleting (chapter 2 gains a section, and its call count",