Add reset-latency StartOS action

Calls POST /api/admin/reset-latency to zero the block-update latency
counters. Available while the service is running, no warning needed.

manifest.yaml

@@ -166,6 +166,14 @@ actions:
       - stopped
     implementation:
       type: script
+  reset-latency:
+    name: "Reset Block Latency"
+    description: "Zeroes the block-update latency counters (avg, last, wasted work, block count). Use this after tuning ZMQ or ckpool to start fresh measurements."
+    warning: ~
+    allowed-statuses:
+      - running
+    implementation:
+      type: script
 
 migrations:
   from:

scripts/procedures/actions.ts

@@ -249,6 +249,46 @@ export const action: T.ExpectedExports.action = {
     };
   },
 
+  // ── Reset block latency ─────────────────────────────────────────────────────
+  "reset-latency": async (effects) => {
+    try {
+      const res = await effects.fetch(`${API_BASE}/api/admin/reset-latency`, {
+        method: "POST",
+      });
+      if (!res.ok) {
+        const body = await res.text();
+        return {
+          result: {
+            version: "0",
+            message: "Failed to reset latency stats",
+            value: `API returned ${res.status}: ${body}`,
+            copyable: false,
+            qr: false,
+          },
+        };
+      }
+    } catch (e) {
+      return {
+        result: {
+          version: "0",
+          message: "Failed — API unreachable",
+          value: `Could not reach kamado-api: ${(e as Error).message}`,
+          copyable: false,
+          qr: false,
+        },
+      };
+    }
+    return {
+      result: {
+        version: "0",
+        message: "Block latency stats reset to zero",
+        value: "All latency counters (count, avg, last, wasted work) have been cleared.\nNew measurements will accumulate from the next block.",
+        copyable: false,
+        qr: false,
+      },
+    };
+  },
+
   // ── Regenerate TLS certificate ──────────────────────────────────────────────
   "regen-tls-cert": async (effects) => {
     const VOLUME = "main";