feat(ui): checkpoints table collapsible, default collapsed

ui/src/pages/AppsTab/AppDeploymentPage/AppDeploymentPage.module.css

@@ -400,3 +400,39 @@
   position: relative;
   z-index: 1;
 }
+
+/* Collapsible Checkpoints header */
+.checkpointsSection {
+  display: flex;
+  flex-direction: column;
+}
+
+.checkpointsHeader {
+  display: inline-flex;
+  align-items: center;
+  gap: 6px;
+  background: none;
+  border: none;
+  padding: 8px 0;
+  font-size: 13px;
+  font-weight: 600;
+  color: var(--text-primary);
+  cursor: pointer;
+  text-align: left;
+}
+
+.checkpointsHeader:hover {
+  color: var(--amber);
+}
+
+.checkpointsChevron {
+  color: var(--text-muted);
+  font-size: 11px;
+  width: 12px;
+  text-align: center;
+}
+
+.checkpointsCount {
+  color: var(--text-muted);
+  font-weight: 400;
+}

ui/src/pages/AppsTab/AppDeploymentPage/CheckpointsTable.test.tsx

@@ -25,10 +25,23 @@ const stoppedDep: Deployment = {
   deployedConfigSnapshot: { jarVersionId: 'v6id', agentConfig: null, containerConfig: {}, sensitiveKeys: null },
 };
 
+function expand() {
+  fireEvent.click(screen.getByRole('button', { name: /checkpoints/i }));
+}
+
 describe('CheckpointsTable', () => {
-  it('renders a row per checkpoint with version, jar, deployer', () => {
+  it('defaults to collapsed — header visible, rows hidden', () => {
     wrap(<CheckpointsTable deployments={[stoppedDep]} versions={[v6]}
       currentDeploymentId={null} jarRetentionCount={5} onSelect={() => {}} />);
+    expect(screen.getByRole('button', { name: /checkpoints \(1\)/i })).toBeInTheDocument();
+    expect(screen.queryByText('v6')).toBeNull();
+    expect(screen.queryByText('my-app-1.2.3.jar')).toBeNull();
+  });
+
+  it('clicking header expands to show rows', () => {
+    wrap(<CheckpointsTable deployments={[stoppedDep]} versions={[v6]}
+      currentDeploymentId={null} jarRetentionCount={5} onSelect={() => {}} />);
+    expand();
     expect(screen.getByText('v6')).toBeInTheDocument();
     expect(screen.getByText('my-app-1.2.3.jar')).toBeInTheDocument();
     expect(screen.getByText('alice')).toBeInTheDocument();
@@ -38,7 +51,7 @@ describe('CheckpointsTable', () => {
     const onSelect = vi.fn();
     wrap(<CheckpointsTable deployments={[stoppedDep]} versions={[v6]}
       currentDeploymentId={null} jarRetentionCount={5} onSelect={onSelect} />);
-    // Use the version text as the row anchor (most stable selector)
+    expand();
     fireEvent.click(screen.getByText('v6').closest('tr')!);
     expect(onSelect).toHaveBeenCalledWith('d1');
   });
@@ -47,6 +60,7 @@ describe('CheckpointsTable', () => {
     const noActor = { ...stoppedDep, createdBy: null };
     wrap(<CheckpointsTable deployments={[noActor]} versions={[v6]}
       currentDeploymentId={null} jarRetentionCount={5} onSelect={() => {}} />);
+    expand();
     expect(screen.getByText('—')).toBeInTheDocument();
   });
 
@@ -54,14 +68,14 @@ describe('CheckpointsTable', () => {
     const pruned = { ...stoppedDep, appVersionId: 'unknown' };
     wrap(<CheckpointsTable deployments={[pruned]} versions={[]}
       currentDeploymentId={null} jarRetentionCount={5} onSelect={() => {}} />);
+    expand();
     expect(screen.getByText(/archived/i)).toBeInTheDocument();
   });
 
-  it('excludes the currently-running deployment', () => {
+  it('renders nothing when there are no checkpoints', () => {
-    wrap(<CheckpointsTable deployments={[stoppedDep]} versions={[v6]}
+    const { container } = wrap(<CheckpointsTable deployments={[stoppedDep]} versions={[v6]}
       currentDeploymentId="d1" jarRetentionCount={5} onSelect={() => {}} />);
-    expect(screen.queryByText('v6')).toBeNull();
+    expect(container).toBeEmptyDOMElement();
-    expect(screen.getByText(/no past deployments/i)).toBeInTheDocument();
   });
 
   it('caps visible rows at jarRetentionCount and shows expander', () => {
@@ -70,7 +84,7 @@ describe('CheckpointsTable', () => {
     }));
     wrap(<CheckpointsTable deployments={many} versions={[v6]}
       currentDeploymentId={null} jarRetentionCount={3} onSelect={() => {}} />);
-    // 3 visible rows + 1 header row = 4 rows max in the table
+    expand();
     expect(screen.getAllByRole('row').length).toBeLessThanOrEqual(4);
     expect(screen.getByText(/show older \(7\)/i)).toBeInTheDocument();
   });
@@ -78,6 +92,7 @@ describe('CheckpointsTable', () => {
   it('shows all rows when jarRetentionCount >= total', () => {
     wrap(<CheckpointsTable deployments={[stoppedDep]} versions={[v6]}
       currentDeploymentId={null} jarRetentionCount={10} onSelect={() => {}} />);
+    expand();
     expect(screen.queryByText(/show older/i)).toBeNull();
   });
 
@@ -87,6 +102,7 @@ describe('CheckpointsTable', () => {
     }));
     wrap(<CheckpointsTable deployments={fifteen} versions={[v6]}
       currentDeploymentId={null} jarRetentionCount={null} onSelect={() => {}} />);
+    expand();
     expect(screen.getByText(/show older \(5\)/i)).toBeInTheDocument();
   });
 });

ui/src/pages/AppsTab/AppDeploymentPage/CheckpointsTable.tsx

@@ -22,6 +22,7 @@ export function CheckpointsTable({
   onSelect,
 }: CheckpointsTableProps) {
   const [expanded, setExpanded] = useState(false);
+  const [open, setOpen] = useState(false);
   const versionMap = new Map(versions.map((v) => [v.id, v]));
 
   const checkpoints = deployments
@@ -37,6 +38,19 @@ export function CheckpointsTable({
   const hidden = checkpoints.length - visible.length;
 
   return (
+    <div className={styles.checkpointsSection}>
+      <button
+        type="button"
+        className={styles.checkpointsHeader}
+        onClick={() => setOpen((v) => !v)}
+        aria-expanded={open}
+      >
+        <span className={styles.checkpointsChevron}>{open ? '\u25BE' : '\u25B8'}</span>
+        <span>Checkpoints</span>
+        {' '}
+        <span className={styles.checkpointsCount}>({checkpoints.length})</span>
+      </button>
+      {open && (
         <div className={styles.checkpointsTable}>
           <table>
             <thead>
@@ -108,5 +122,7 @@ export function CheckpointsTable({
             </button>
           )}
         </div>
+      )}
+    </div>
   );
 }