feat(phase987): mesh stability UI bandwidth diagnostics journey stub

Adds runMeshStabilityUiBandwidthDiagnosticsJourney for agentctl smoke coverage.
Non-breaking headless journey only.

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

headless.js

@@ -1817,6 +1817,30 @@ class HeadlessSession {
     return { multi, federation }
   }
 
+  /** Journey stub: mesh stability UI bandwidth diagnostics keys + embed snapshot (Phase 987). */
+  async runMeshStabilityUiBandwidthDiagnosticsJourney (guildId) {
+    if (!this.platform) throw new Error('headless not started')
+    const gid = guildId || this.platform.guild?.guild?.id
+    if (!gid) throw new Error('no guild')
+    const path = require('bare-path')
+    const {
+      listMeshStabilityUiBandwidthDiagnosticsFieldKeys,
+      buildMeshStabilityBandwidthDiagnosticsSnapshot
+    } = require('pearcord-platform/mesh-stability-ui-bandwidth-diagnostics-keys')
+    const uiPath = path.join(__dirname, '..', '..', 'apps', 'pearcord', 'ui', 'mesh-stability-ui-bandwidth-diagnostics.js')
+    const { buildMeshStabilityBandwidthDiagnosticsEmbedHtml } = await import(uiPath)
+    const view = await this.refreshView()
+    const fields = listMeshStabilityUiBandwidthDiagnosticsFieldKeys()
+    const mss = view?.meshStabilityStats || {}
+    const snapshot = buildMeshStabilityBandwidthDiagnosticsSnapshot(mss)
+    const embedHtml = buildMeshStabilityBandwidthDiagnosticsEmbedHtml({
+      ...mss,
+      bandwidthCapEffective: mss.bandwidthCapEffective || 1024,
+      bandwidthUsedBytes: mss.bandwidthUsedBytes || 512
+    })
+    return { guildId: gid, fields, snapshot, embedHtml, view }
+  }
+
   /** Journey stub: mesh stability UI diagnostics IPC keys + snapshot (Phase 986). */
   async runMeshStabilityUiDiagnosticsIpcJourney (guildId) {
     if (!this.platform) throw new Error('headless not started')