feat(rust): the rewards — tally, kit reward, chat and the news leg (phase 13b, protocol 10)

Four event verbs and the announce leg, per PLAN.md §29:

- rust.participation.open / .collect: the plugin counts who takes part
  (seconds, kills or both, in a zone this run opened or the whole server)
  and collect files them as the run's participants, keyed by Steam id.
- rust.kit.entitle: the five recipient modes (D101), rows in the new
  rust_perm_run_grants (D84) unioned into the permission push, one extra
  use of the kit per reward as site-held credits on perm.sync (D103),
  and the rust.kit.entitled notice deferred from phase 10 (D64).
- rust.announce: one server or every server (D105).
- rust.chat announce leg, speaking only on servers whose new news switch
  is on (D104) - a card on Admin -> Rust visibility (D106).

Budgets rust.grants and rust.announcements; the kit source and four
fixed-choice sources (core has no enum param type). rust_perm_run_grants
carries core's idempotency key so a revert of a lost answer can find its
rows. Protocol 10.

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

server/db/purge.sql

@@ -19,6 +19,9 @@
 -- it knows this module registered, because it is the side that knows which
 -- registrant owned what.
 
+-- Phase 13b.
+DROP TABLE IF EXISTS rust_perm_run_grants;
+
 -- Phase 7b.
 DROP TABLE IF EXISTS rust_clan_boards;
 DROP TABLE IF EXISTS rust_clan_members;