Center the login gate so the password field is not a full-width strip.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/HSchool.Client/src/style.css

@@ -63,6 +63,35 @@ body {
   justify-content: center;
 }
 
+/*
+ * Phase 38 dropped the gate in as a full-width .screen and never gave it a column. Without a cap
+ * the password field spans the window; without centering it clings to the top-left. Same tokens as
+ * .dialog — this is one short form, not a management screen.
+ */
+.screen.session-gate {
+  align-items: center;
+  justify-content: center;
+}
+
+.session-gate__panel {
+  display: flex;
+  flex-direction: column;
+  gap: 16px;
+  width: min(360px, 100%);
+  padding: 24px;
+  border: 1px solid var(--border);
+  border-radius: 14px;
+  background: var(--surface-raised);
+}
+
+.session-gate .form {
+  width: 100%;
+}
+
+.session-gate .button {
+  align-self: flex-start;
+}
+
 /*
  * No cap. A reading column has a sensible maximum width; a management screen does not — it is a
  * tree, a table and a timetable grid, and every pixel taken away from them is a pixel of scrolling.

src/HSchool.Client/src/ui/sessionGate.test.ts

@@ -37,4 +37,19 @@ describe('session gate', () => {
 
     pending.catch(() => undefined);
   });
+
+  it('mounts a centred panel and the shared input class, not a raw full-width field', async () => {
+    vi.mocked(fetchSession).mockRejectedValue(new ApiError(401, 'unknown', 'Unauthorized'));
+
+    const pending = ensureSession();
+    await Promise.resolve();
+
+    const gate = document.querySelector('.session-gate');
+    const password = document.querySelector<HTMLInputElement>('.session-gate input[type="password"]');
+    expect(gate?.querySelector('.session-gate__panel')).not.toBeNull();
+    expect(password?.className).toBe('input');
+    expect(password?.className).not.toContain('field__input');
+
+    pending.catch(() => undefined);
+  });
 });

src/HSchool.Client/src/ui/sessionGate.ts

@@ -27,16 +27,17 @@ function showSessionGate(): Promise<string> {
   return new Promise((resolve) => {
     let password = '';
     const root = el('section', { class: 'screen session-gate' });
+    const panel = el('div', { class: 'session-gate__panel' });
     const title = el('h1', { class: 'screen__title' });
     const passwordLabel = el('label', { class: 'field' });
     const passwordInput = el('input', {
-      class: 'field__input',
+      class: 'input',
       type: 'password',
       autocomplete: 'current-password',
     }) as HTMLInputElement;
     const nameLabel = el('label', { class: 'field' });
     const nameInput = el('input', {
-      class: 'field__input',
+      class: 'input',
       type: 'text',
       autocomplete: 'username',
       maxlength: '40',
@@ -51,7 +52,7 @@ function showSessionGate(): Promise<string> {
 
     const form = el(
       'form',
-      { class: 'session-gate__form' },
+      { class: 'form' },
       passwordLabel,
       nameLabel,
       error,
@@ -63,7 +64,8 @@ function showSessionGate(): Promise<string> {
       void submitStep();
     });
 
-    root.append(title, form);
+    panel.append(title, form);
+    root.append(panel);
     app.replaceChildren(root);
     paint();