feat(discord): eyes reaction as a read receipt on every admitted message (#1509)

QUEUE row 15, MVP iteration 1 after the Sage pilot. rest.react is best
effort (2xx true, anything else false, never throws); the connector reacts
at admission before the engine runs and records the outcome in the turn
record as receipt. Drops and refusals get no reaction. Suite 28/28, 90
node tests.

Co-Authored-By: Claude Fable 5.1 <[email protected]>

packages/discord/tests/helpers.mjs

@@ -100,6 +100,9 @@ export function fakeRest({ outcomes = [] } = {}) {
   return {
     calls,
     typingCalls: [],
+    reactions: [],
+    // When false, react resolves false (Discord refused the reaction).
+    reactOk: true,
     channels: new Map(),
     lookups: 0,
     // When set, getChannel waits on this promise before answering (held lookup).
@@ -116,6 +119,10 @@ export function fakeRest({ outcomes = [] } = {}) {
     async typing(channelId) {
       this.typingCalls.push(channelId);
     },
+    async react(channelId, messageId, emoji) {
+      this.reactions.push({ channelId, messageId, emoji });
+      return this.reactOk;
+    },
     async getChannel(id) {
       this.lookups += 1;
       if (this.holdLookup) await this.holdLookup;