Improve agentless mode messaging for host-level metrics

Updated the messaging and UI to clarify unavailability of host-level metrics, such as CPU, RAM, and disk space, in agentless mode. Added clear formatting and new functions to handle missing metrics gracefully in the frontend.

backend/app/services/infra_probe.py

@@ -17,10 +17,10 @@ class DiskSpaceProvider:
 class NullDiskSpaceProvider(DiskSpaceProvider):
     async def get_free_bytes(self, target_host: str) -> DiskSpaceProbeResult:
         return DiskSpaceProbeResult(
-            source="none",
+            source="agentless",
             status="unavailable",
             free_bytes=None,
-            message=f"No infra probe configured for host {target_host}. Add SSH/Agent provider later.",
+            message=f"Agentless mode: host-level free disk is not available for {target_host}.",
         )
 
 

frontend/src/pages/TargetDetailPage.jsx

@@ -41,6 +41,19 @@ function formatNumber(value, digits = 2) {
   return Number(value).toFixed(digits);
 }
 
+function formatHostMetricUnavailable() {
+  return "N/A (agentless)";
+}
+
+function formatDiskSpaceAgentless(diskSpace) {
+  if (!diskSpace) return formatHostMetricUnavailable();
+  if (diskSpace.free_bytes !== null && diskSpace.free_bytes !== undefined) {
+    return formatBytes(diskSpace.free_bytes);
+  }
+  if (diskSpace.status === "unavailable") return formatHostMetricUnavailable();
+  return "-";
+}
+
 function MetricsTooltip({ active, payload, label }) {
   if (!active || !payload || payload.length === 0) return null;
   const row = payload[0]?.payload || {};
@@ -346,6 +359,9 @@ export function TargetDetailPage() {
       {uiMode === "dba" && overview && (
         <div className="card">
           <h3>Database Overview</h3>
+          <p className="muted" style={{ marginTop: 2 }}>
+            Agentless mode: host-level CPU, RAM, and free-disk metrics are not available.
+          </p>
           <div className="grid three overview-kv">
             <div><span>PostgreSQL Version</span><strong>{overview.instance.server_version || "-"}</strong></div>
             <div>
@@ -366,8 +382,8 @@ export function TargetDetailPage() {
             <div title="Total WAL directory size (when available)">
               <span>WAL Size</span><strong>{formatBytes(overview.storage.wal_directory_size_bytes)}</strong>
             </div>
-            <div title="Optional metric via future Agent/SSH provider">
-              <span>Free Disk</span><strong>{formatBytes(overview.storage.disk_space.free_bytes)}</strong>
+            <div title={overview.storage.disk_space?.message || "Agentless mode: host-level free disk is unavailable."}>
+              <span>Free Disk</span><strong>{formatDiskSpaceAgentless(overview.storage.disk_space)}</strong>
             </div>
             <div title="Replication replay delay on standby">
               <span>Replay Lag</span>
@@ -378,6 +394,12 @@ export function TargetDetailPage() {
             <div><span>Replication Slots</span><strong>{overview.replication.replication_slots_count ?? "-"}</strong></div>
             <div><span>Repl Clients</span><strong>{overview.replication.active_replication_clients ?? "-"}</strong></div>
             <div><span>Autovacuum Workers</span><strong>{overview.performance.autovacuum_workers ?? "-"}</strong></div>
+            <div title="Host CPU requires OS-level telemetry">
+              <span>Host CPU</span><strong>{formatHostMetricUnavailable()}</strong>
+            </div>
+            <div title="Host RAM requires OS-level telemetry">
+              <span>Host RAM</span><strong>{formatHostMetricUnavailable()}</strong>
+            </div>
           </div>
 
           <div className="grid two">