Phase 719: read state and webhook execute JSON mesh parity (v0.8.695)

Add dedicated signed-export modals for read receipts and webhook execute
exports, populate view rows and meta, partition-heal mixins with dedicated
spans, agentctl journeys, and CI smokes following the Phase 718 pattern.

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

headless.js

@@ -4445,6 +4445,40 @@ class HeadlessSession {
     }
   }
 
+  async runReadStateExportJsonJourney () {
+    if (!this.platform) throw new Error('headless not started')
+    await this.registerUser({ username: 'rs719', displayName: 'Read State 719' })
+    await this.createGuild({ name: 'Read State 719', publicListing: false })
+    await this.wait({ mode: 'guild' }, 45000)
+    await this.refreshView()
+    const pushed = await this.platform.pushReadStateExportToMesh()
+    const v = await this.refreshView()
+    if (!pushed?.signature && !v.readStateExportJsonMeta?.signature) {
+      throw new Error('expected signed read state export JSON after mesh push')
+    }
+    return {
+      guildReadStateJsonCount: v.guildReadStateJsonCount || (v.readStateExportJsonRows || []).length,
+      hasMeta: v.readStateExportJsonMeta != null
+    }
+  }
+
+  async runWebhookExecuteExportJsonJourney () {
+    if (!this.platform) throw new Error('headless not started')
+    await this.registerUser({ username: 'wh719', displayName: 'Webhook 719' })
+    await this.createGuild({ name: 'Webhook 719', publicListing: false })
+    await this.wait({ mode: 'guild' }, 45000)
+    await this.refreshView()
+    const pushed = await this.platform.pushWebhookExecuteExportToMesh()
+    const v = await this.refreshView()
+    if (!pushed?.signature && !v.webhookExecuteExportJsonMeta?.signature) {
+      throw new Error('expected signed webhook execute export JSON after mesh push')
+    }
+    return {
+      guildWebhookExecuteJsonCount: v.guildWebhookExecuteJsonCount || (v.webhookExecuteExportJsonRows || []).length,
+      hasMeta: v.webhookExecuteExportJsonMeta != null
+    }
+  }
+
   async runForumPostSearchJourney () {
     if (!this.platform) throw new Error('headless not started')
     await this.registerUser({ username: 'fm672', displayName: 'Forum 672' })