fix(admin): clear baselineMbps on delete/clear so Avg Baseline doesn't linger

The "Avg Baseline" header stat is computed from baselineHistory, falling back to
state.baselineMbps when the history is empty. clearActiveRunView (delete-active)
and /api/clear cleared baselineHistory/nodeSpeedHistory but NOT baselineMbps — so
after deleting a run the stat fell back to the deleted run's baseline and kept
showing it. Null baselineMbps in both wipe paths (mirrors the baselineHistory
clearing already there). Test suite green (188/31/45/35).

Author: Sentinel-Bluebuilder

server.js

@@ -1006,6 +1006,10 @@ function clearActiveRunView() {
   // activeBatchId/resumeHeadAddr could mis-target a later resume.
   state.baselineHistory = [];
   state.nodeSpeedHistory = [];
+  // Also clear the single current-baseline value — the "Avg Baseline" header
+  // stat falls back to baselineMbps when baselineHistory is empty, so without
+  // this the DELETED run's baseline keeps showing after a delete.
+  state.baselineMbps = null;
   state.currentNode = null;
   state.resumeHeadAddr = null;
   state.activeBatchId = 0;
@@ -2738,6 +2742,7 @@ app.post('/api/clear', adminOnly, (req, res) => {
   state.retryCount = 0;
   state.baselineHistory = [];
   state.nodeSpeedHistory = [];
+  state.baselineMbps = null; // else "Avg Baseline" falls back to the stale value
   // /api/clear wipes the DISPLAYED rows but keeps the active-run identity
   // (activeRunNumber / activeDbRunId / pipeline run dir stay attached — use
   // clearActiveRunView()/deleteRun to drop the identity). The counters above