feat(platform): Phase 112 relay signing and health decay

- Sign relay handoffs with guild-derived secret for webhook/smtp plugins
- Verify signature on getLastDigestRelayHandoff (signatureValid)
- Apply health decay in archive peer picker
- Show signature status in server settings UI

Co-authored-by: Cursor <[email protected]>

index.js

@@ -52,6 +52,7 @@ const {
   buildDigestRelayHandoff,
   formatHookFailureDigestDmSummary,
   computeArchivePeerHealthScore,
+  applyArchivePeerHealthDecay,
   computeArchiveFetchBackoffMs,
   HookFailureAlertStore
 } = require('pearcord-delivery-receipts')
@@ -67,6 +68,7 @@ const {
 } = require('pearcord-integration-worker')
 const {
   applyRelayPluginToHandoff,
+  verifyDigestRelayHandoff,
   listBuiltinDigestRelayPlugins
 } = require('pearcord-digest-relay-plugin')
 const { PearcordIntegrationWorker } = require('./integration-worker')
@@ -2198,7 +2200,7 @@ class PearcordPlatform extends EventEmitter {
         presenceSeen.get(userId) || 0,
         stored?.lastSeenAt || 0
       ) || null
-      const health =
+      const baseHealth =
         stored?.healthScore != null
           ? {
               score: stored.healthScore,
@@ -2209,6 +2211,7 @@ class PearcordPlatform extends EventEmitter {
               online: presenceOnline || (userId === selfId && meshLive),
               lastSeenAt
             })
+      const health = applyArchivePeerHealthDecay(baseHealth, { lastSeenAt })
       options.push({
         memberId: userId,
         label: userId === selfId ? `${name} (you)` : name,
@@ -2217,6 +2220,7 @@ class PearcordPlatform extends EventEmitter {
         lastSeenAt,
         healthScore: health.score,
         healthLabel: health.label,
+        healthDecayed: !!health.decayed,
         isSelf: userId === selfId
       })
     }
@@ -2672,7 +2676,12 @@ class PearcordPlatform extends EventEmitter {
   async getLastDigestRelayHandoff () {
     if (!this.guild?.guild) return null
     await this._initDeliveryReceipts(this.guild.guild.id)
-    return this.deliveryReceipts.getLastDigestRelayHandoff()
+    const handoff = await this.deliveryReceipts.getLastDigestRelayHandoff()
+    if (!handoff?.signature) return handoff
+    const verified = verifyDigestRelayHandoff(handoff, {
+      relaySecret: this.guild.guild.id
+    })
+    return { ...handoff, signatureValid: verified.ok }
   }
 
   async getAutomationDigestNotifyPrefs () {
@@ -2823,7 +2832,11 @@ class PearcordPlatform extends EventEmitter {
       snapshot: snap
     })
     const plugin = await this.deliveryReceipts.getActiveDigestRelayPlugin()
-    if (plugin) handoff = applyRelayPluginToHandoff(handoff, plugin)
+    if (plugin) {
+      handoff = applyRelayPluginToHandoff(handoff, plugin, {
+        relaySecret: this.guild.guild.id
+      })
+    }
     await this.deliveryReceipts.appendDigestRelayHandoff(handoff)
     this.emit('digest-relay-handoff', handoff)
     return handoff