feat(ui/alerts): TriggerStep (evaluation interval, for-duration, re-notify, test-evaluate)

Three numeric inputs for evaluation cadence, for-duration, and
re-notification window, plus a Test evaluate button for saved rules.
TestEvaluateRequest is empty on the wire (server uses the rule id), so
we send {} and rely on the backend to evaluate the current saved state.

Deviation: plan draft passed {condition: toRequest(form).condition} into
the request body. The generated TestEvaluateRequest type is
Record<string, never>, so we send an empty body.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

ui/src/pages/Alerts/RuleEditor/TriggerStep.tsx

@@ -1,13 +1,85 @@
+import { useState } from 'react';
+import { Button, FormField, Input, useToast } from '@cameleer/design-system';
+import { useTestEvaluate } from '../../../api/queries/alertRules';
 import type { FormState } from './form-state';
 
 export function TriggerStep({
-  form: _form,
-  setForm: _setForm,
-  ruleId: _ruleId,
+  form,
+  setForm,
+  ruleId,
 }: {
   form: FormState;
   setForm: (f: FormState) => void;
   ruleId?: string;
 }) {
-  return <div>Trigger step &mdash; TODO Task 22</div>;
+  const testEvaluate = useTestEvaluate();
+  const { toast } = useToast();
+  const [lastResult, setLastResult] = useState<string | null>(null);
+
+  const onTest = async () => {
+    if (!ruleId) {
+      toast({ title: 'Save rule first to run test evaluate', variant: 'error' });
+      return;
+    }
+    try {
+      const result = await testEvaluate.mutateAsync({ id: ruleId, req: {} });
+      setLastResult(JSON.stringify(result, null, 2));
+    } catch (e) {
+      toast({ title: 'Test-evaluate failed', description: String(e), variant: 'error' });
+    }
+  };
+
+  return (
+    <div style={{ display: 'grid', gap: 12, maxWidth: 600 }}>
+      <FormField label="Evaluation interval (seconds, min 5)">
+        <Input
+          type="number"
+          min={5}
+          value={form.evaluationIntervalSeconds}
+          onChange={(e) => setForm({ ...form, evaluationIntervalSeconds: Number(e.target.value) })}
+        />
+      </FormField>
+      <FormField label="For-duration before firing (seconds, 0 = fire immediately)">
+        <Input
+          type="number"
+          min={0}
+          value={form.forDurationSeconds}
+          onChange={(e) => setForm({ ...form, forDurationSeconds: Number(e.target.value) })}
+        />
+      </FormField>
+      <FormField label="Re-notify cadence (minutes, 0 = notify once)">
+        <Input
+          type="number"
+          min={0}
+          value={form.reNotifyMinutes}
+          onChange={(e) => setForm({ ...form, reNotifyMinutes: Number(e.target.value) })}
+        />
+      </FormField>
+      <div>
+        <Button variant="secondary" onClick={onTest} disabled={testEvaluate.isPending}>
+          Test evaluate (uses saved rule)
+        </Button>
+        {!ruleId && (
+          <p style={{ marginTop: 8, fontSize: 12, color: 'var(--muted)' }}>
+            Save the rule first to enable test-evaluate.
+          </p>
+        )}
+        {lastResult && (
+          <pre
+            style={{
+              marginTop: 12,
+              padding: 8,
+              background: 'var(--code-bg)',
+              borderRadius: 6,
+              fontSize: 12,
+              maxHeight: 240,
+              overflow: 'auto',
+            }}
+          >
+            {lastResult}
+          </pre>
+        )}
+      </div>
+    </div>
+  );
 }