fix(drain): don't claim acceptance with nothing evicted; latch plan-unsupported

The drain toast appended "evictions were accepted" even when every
eviction failed or only skips happened, contradicting its own title.
It now says that only when at least one pod was actually evicted; the
node-stays-cordoned note is unconditional.

The plan-unsupported fallback came straight from the current mutation
error, which the next request clears, so toggling an option refired a
request known to 404 and bounced the dialog out of fallback mode. The
dialog now latches unsupported for as long as it stays open and stops
refetching while latched.

Claude-Session: https://claude.ai/code/session_01NE55VsYGkb5tV3neKDmtZw

Author: hisco

packages/k8s-ui/src/components/shared/ResourceActionsBar.tsx

@@ -198,13 +198,26 @@ export function ResourceActionsBar({
   const [showDrainConfirm, setShowDrainConfirm] = useState(false)
   const [drainOptions, setDrainOptions] = useState<DrainDialogOptions>(DEFAULT_DRAIN_DIALOG_OPTIONS)
 
+  // A backend without the plan endpoint stays unsupported for as long as the dialog is
+  // open: the host reports it through a mutation error, which the next request clears,
+  // so without latching every option change would refire a request known to 404 and
+  // bounce the dialog out of its fallback mode.
+  const [planUnsupported, setPlanUnsupported] = useState(false)
+  useEffect(() => {
+    if (drainPlanUnsupported) setPlanUnsupported(true)
+  }, [drainPlanUnsupported])
+  useEffect(() => {
+    if (!showDrainConfirm) setPlanUnsupported(false)
+  }, [showDrainConfirm])
+  const planSupported = Boolean(onPlanDrain) && !planUnsupported
+
   // Fetch (and refetch on option changes) the read-only plan while the drain dialog is open.
   useEffect(() => {
-    if (showDrainConfirm && onPlanDrain) {
+    if (showDrainConfirm && onPlanDrain && !planUnsupported) {
       onPlanDrain({ name: resource.name, options: drainOptions })
     }
     // eslint-disable-next-line react-hooks/exhaustive-deps
-  }, [showDrainConfirm, drainOptions.force, drainOptions.deleteEmptyDirData, resource.name])
+  }, [showDrainConfirm, drainOptions.force, drainOptions.deleteEmptyDirData, resource.name, planUnsupported])
 
   // Rollback dialog state
   const [showRevisions, setShowRevisions] = useState(false)
@@ -702,11 +715,11 @@ export function ResourceActionsBar({
         nodeName={resource.name}
         plan={drainPlan}
         loading={Boolean(isPlanningDrain)}
-        error={drainPlanUnsupported ? null : drainPlanError}
+        error={planSupported ? drainPlanError : null}
         options={drainOptions}
         onOptionsChange={setDrainOptions}
-        planSupported={Boolean(onPlanDrain) && !drainPlanUnsupported}
-        onRefreshPlan={onPlanDrain ? () => onPlanDrain({ name: resource.name, options: drainOptions }) : undefined}
+        planSupported={planSupported}
+        onRefreshPlan={planSupported ? () => onPlanDrain?.({ name: resource.name, options: drainOptions }) : undefined}
         isDraining={Boolean(isDrainingNode)}
         onClose={() => {
           setShowDrainConfirm(false)

web/src/api/client.ts

@@ -5213,7 +5213,9 @@ export function describeDrainResult(data: {
     parts.push(`Failed ${errors.length}: ${listWithOverflow(errors)}`);
   }
   parts.push(
-    "Evictions were accepted; pods may still be terminating. The node remains cordoned.",
+    evicted > 0
+      ? "Evictions were accepted; those pods may still be terminating. The node remains cordoned."
+      : "The node remains cordoned.",
   );
   const detail = parts.join("\n");
   if (errors.length > 0) {

web/src/api/drain-plan.test.ts

@@ -63,7 +63,24 @@ describe("describeDrainResult", () => {
     const r = describeDrainResult({ evictedPods: ["a", "b"] });
     expect(r.failed).toBe(false);
     expect(r.title).toBe("Node drained: 2 evicted, 0 skipped");
-    expect(r.detail).toContain("pods may still be terminating");
+    expect(r.detail).toContain("those pods may still be terminating");
     expect(r.detail).toContain("node remains cordoned");
   });
+
+  it("never claims evictions were accepted when nothing was evicted", () => {
+    const allFailed = describeDrainResult({
+      evictedPods: [],
+      errors: ["shop/web-1: timed out waiting for PDB to allow eviction"],
+    });
+    expect(allFailed.detail).not.toContain("accepted");
+    expect(allFailed.detail).toContain("node remains cordoned");
+
+    const skipOnly = describeDrainResult({
+      evictedPods: [],
+      skippedPods: [
+        { namespace: "shop", name: "agent", outcome: "skip", reason: "managed by a DaemonSet", emptyDir: false, pdbChecked: false },
+      ],
+    });
+    expect(skipOnly.detail).not.toContain("accepted");
+  });
 });