feat(events): a dry run carries a module's advice (MODULE_API 1.16.0)

An action answering verify: true with { ok: true, detail: { warnings } } has
each line shown as a warning finding (code `advice`) that never fails the
dry run. Strings only, at most ten per step, each cut at 500 characters;
anything else under warnings is ignored, and a refused step carries none.

Rust PLAN_REDESIGNS §11.4, D391: a raid base's spot is checked against the
world as it stands now (a player on it, a rock beside it), which may change
before the run, so the editor shows it as advice. One optional reading of an
existing member, so minor; Module-uo's ^1.10.0 still resolves and says no
warnings. STEAM_SIGNIN.md's claim moves to 1.17.0.

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

server/engagement-triggers.json

@@ -1,6 +1,6 @@
 {
   "_comment": "Generated event-trigger inventory - the authoritative freeze of CORE's engagement contract (docs/website/ENGAGEMENT.md 4.3). Regenerate with `npm run engagement:manifest` in website/server. A renamed variable, a changed type or a widened ceiling breaks stored templates and rules, so the diff here is the review signal. A module ships its own copy in its bundle; this file never contains one.",
-  "moduleApiVersion": "1.15.0",
+  "moduleApiVersion": "1.16.0",
   "triggers": [
     {
       "id": "event.phase.changed",