feat(rust): Guarded Crate — feed, map, Warden, Place a guarded crate (PLAN_REDESIGNS §14.3.5)

Stage 6 of the §14.3 integration plan, on protocol 14. Spec: docs
rust-link/PROTOCOL.md §20.9.

- gc.started and gc.ended public, gc.failed staff's; guardedCrate.js reads
  each row per viewer (the clearer's name for the presence audience, Steam id,
  position and key for staff, `won` for everyone).
- Triggers rust.gc.started and rust.gc.ended (a crate a player cleared only).
- The step rust.gc.place: an event from rust.options.gc_events and a world
  call's location; refused at verify for Guarded Crate absent, NpcSpawn missing
  (D364), console unavailable, or an unknown event. Kept (D373); the run log's
  success line says so (D380). Budget rust.gc.crates.
- Warden (D375): guarded_won, title category guardedwon, Crates cleared column.
- Map marker, server settings line, swagger, engagement manifest, bundle, README.

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

server/engagement/emit.js

@@ -187,6 +187,15 @@ const HEADLINES = Object.freeze({
     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` : ''}.`,
   }),
+  // Guarded Crate (protocol 14, §14.3.5). A missing grid drops out.
+  'rust.gc.started': (d) => ({
+    title: `A guarded crate landed on ${d.server}`,
+    intro: `A guarded crate landed${d.grid ? ` at ${d.grid}` : ''} on ${d.server}. Kill its guards to claim it.`,
+  }),
+  'rust.gc.ended': (d) => ({
+    title: `The guarded crate was cleared on ${d.server}`,
+    intro: `${d.player} cleared the guarded crate${d.grid ? ` at ${d.grid}` : ''} on ${d.server}.`,
+  }),
   'rust.boss.killed': (d) => ({
     title: `${d.boss} was killed on ${d.server}`,
     intro: `${d.killer ? `${d.killer} landed the killing blow` : `${d.boss} fell`}`
@@ -605,9 +614,41 @@ async function onDangerousTreasures(server, item, frame) {
   }) ? 1 : 0
 }
 
+/**
+ * Guarded Crate (protocol 14, §14.3.5): a crate landed, and one cleared. As a
+ * treasure's are: public news, a replay past a broadcast's window tells nobody
+ * (D63), the clearer by in-game name only. An ending with nobody named, and a
+ * timeout, raise nothing.
+ */
+async function onGuardedCrate(server, item, frame) {
+  const t = frameTime(item, frame)
+  if (!stillNews(t, BROADCAST_MAX_AGE_MS)) return 0
+  if (frame.kind === 'gc.ended' && !str(frame.name)) 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 === 'gc.started') {
+    return fire(T['rust.gc.started'], {
+      data: { ...data, byEvent: Boolean(str(frame.key)) },
+      dedupeKey: dedupeKey('gc.started', server.id, t, frame.x, frame.z),
+      occurredAt: t,
+    }) ? 1 : 0
+  }
+
+  return fire(T['rust.gc.ended'], {
+    data: { ...data, player: str(frame.name) },
+    dedupeKey: dedupeKey('gc.ended', server.id, t, frame.steamId, frame.x, frame.z),
+    occurredAt: t,
+  }) ? 1 : 0
+}
+
 const HANDLERS = Object.freeze({
   'dt.started': onDangerousTreasures,
   'dt.won': onDangerousTreasures,
+  'gc.started': onGuardedCrate,
+  'gc.ended': onGuardedCrate,
   'world.event': onWorld,
   'npc.boss.spawned': onBoss,
   'npc.boss.phase': onBoss,