feat(rust): Dangerous Treasures — feed, map, Treasure Hunter, Start a Dangerous Treasures event (PLAN_REDESIGNS §14.3.4)

Stage 5 of the §14.3 integration plan, on protocol 14 (docs
rust-link/PROTOCOL.md §20.8).

- dt.started and dt.won are public kinds, dt.ended a staff kind. The new
  dangerousTreasures.js reads each row per viewer: grid and invaderCount for
  everyone, the winner's name for the presence audience (D376), the position,
  the step's key, the winner's Steam id and the invaders for staff.
- Feed lines in the World events filter: "A Dangerous Treasures event has
  started · K12", "Alice won the treasure · K12 · 3 players fought for it".
- Triggers rust.dt.started (with byEvent) and rust.dt.won, public, cooldown
  subject the server, names only.
- eventDangerousTreasures.js: rust.dt.start, "Start a Dangerous Treasures
  event" (risk change, reversible none, budget rust.dt.events), server and
  difficulty. Refused at verify where the server said DT is not loaded or
  console.plugins is false (Rust-Plugins#34). dt-not-ready answers "Dangerous
  Treasures is not ready yet" with retryAfterMs 600000 (D365, D371);
  dt-no-spot retries on core's delay; DT's own refusals are permanent.
- Treasure Hunter (D375): treasuresWon -> treasures_won, the title category
  treasureswon, and a sortable Treasures column shown where the server
  reports DT or a row counts one.
- The map draws a running chest on the world layer; the server settings'
  plugin line names DT and whether a step can start one, from the
  integrations read's new `console`.
- coreApi ^1.15.0, ci/core-ref.json pinned to website main at #215's merge.
  ci/bundle.json ships the two new files; swagger fragment and engagement
  manifest regenerated; README lists DT.

Server 627/627 (16 new in test/dangerousTreasures.test.js) and every check;
client 92/92, build and externals. Booted against the pinned core: 45
triggers, 13 actions, 11 budgets, 21 option sources; 89 routes unchanged.

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

server/engagement/emit.js

@@ -177,6 +177,16 @@ const HEADLINES = Object.freeze({
     title: `${d.boss} is down to ${d.percent}% on ${d.server}`,
     intro: `${d.boss} fell to ${d.percent}% of its health on ${d.server} and entered phase ${d.phase}.`,
   }),
+  // Dangerous Treasures (protocol 14, §14.3.4). A missing grid drops out.
+  'rust.dt.started': (d) => ({
+    title: `A treasure event has started on ${d.server}`,
+    intro: `A Dangerous Treasures chest opened${d.grid ? ` at ${d.grid}` : ''} on ${d.server}. It is guarded, and it is burning.`,
+  }),
+  'rust.dt.won': (d) => ({
+    title: `The treasure was won on ${d.server}`,
+    intro: `${d.player || 'Somebody'} won the treasure${d.grid ? ` at ${d.grid}` : ''} on ${d.server}`
+      + `${d.invaders > 1 ? `, with ${d.invaders} players fighting for it` : ''}.`,
+  }),
   'rust.boss.killed': (d) => ({
     title: `${d.boss} was killed on ${d.server}`,
     intro: `${d.killer ? `${d.killer} landed the killing blow` : `${d.boss} fell`}`
@@ -561,7 +571,43 @@ async function onWorld(server, item, frame) {
   }) ? 1 : 0
 }
 
+/**
+ * Dangerous Treasures (protocol 14, §14.3.4): a chest opened, and one won.
+ * Public news, so a replay older than a broadcast's window tells nobody (D63).
+ * The grid comes from the map's geometry, as the feed's does; the winner by
+ * in-game name only, never a Steam id. An ending raises nothing.
+ */
+async function onDangerousTreasures(server, item, frame) {
+  const t = frameTime(item, frame)
+  if (!stillNews(t, BROADCAST_MAX_AGE_MS)) return 0
+
+  const meta = frame.x !== undefined ? await mapDb.getMeta(server.id).catch(() => null) : null
+  const grid = meta ? worldEvents.gridOf({ worldSize: Number(meta.worldSize), gridCells: Number(meta.gridCells), gridCellSize: Number(meta.gridCellSize) }, frame.x, frame.z) : null
+  const data = { ...serverVars(server), subject: `${server.id}:${frame.kind}`, ...(grid ? { grid } : {}) }
+
+  if (frame.kind === 'dt.started') {
+    return fire(T['rust.dt.started'], {
+      data: { ...data, byEvent: Boolean(str(frame.key)) },
+      dedupeKey: dedupeKey('dt.started', server.id, t, frame.x, frame.z),
+      occurredAt: t,
+    }) ? 1 : 0
+  }
+
+  const invaders = Number(frame.invaderCount)
+  return fire(T['rust.dt.won'], {
+    data: {
+      ...data,
+      ...(str(frame.name) ? { player: str(frame.name) } : {}),
+      invaders: Number.isInteger(invaders) && invaders >= 0 ? invaders : Array.isArray(frame.invaders) ? frame.invaders.length : 0,
+    },
+    dedupeKey: dedupeKey('dt.won', server.id, t, frame.steamId, frame.x, frame.z),
+    occurredAt: t,
+  }) ? 1 : 0
+}
+
 const HANDLERS = Object.freeze({
+  'dt.started': onDangerousTreasures,
+  'dt.won': onDangerousTreasures,
   'world.event': onWorld,
   'npc.boss.spawned': onBoss,
   'npc.boss.phase': onBoss,