fix(admin): move message row actions into a rightmost column

Add a dedicated operations column for viewing, marking read and deleting
messages. Keep the message cell focused on its title, excerpt and ID;
adjust column widths and empty-state colspan with regression coverage.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/widget-system/message-admin-contract.test.cjs

@@ -80,6 +80,24 @@ test('list toolbar is merged into the table card and inline confirmation is remo
   assert.match(empty, /当前筛选条件下没有消息/);
 });
 
+test('message row actions live only in a dedicated rightmost operations column', () => {
+  const { table, empty } = harness();
+  assert.match(table, /<th scope="col" class="column-time">发送时间<\/th><th scope="col" class="column-actions">操作<\/th><\/tr>/);
+  const rows = [...table.matchAll(/<tr class="is-(?:unread|read)">([\s\S]*?)<\/tr>/g)];
+  assert.equal(rows.length, 2);
+  rows.forEach(([, row]) => {
+    const cells = [...row.matchAll(/<(?:th|td)\b[^>]*>[\s\S]*?<\/(?:th|td)>/g)].map(([cell]) => cell);
+    assert.equal(cells.length, 7);
+    assert.match(cells[1], /class="column-title"/);
+    assert.doesNotMatch(cells[1], /<button|data-aksrt-msg-view|data-aksrt-msg-action/);
+    assert.match(cells[5], /class="column-time"/);
+    assert.match(cells[6], /class="column-actions"/);
+    assert.match(cells[6], /data-aksrt-msg-view=/);
+    assert.match(cells[6], /data-aksrt-msg-action="delete"/);
+  });
+  assert.match(empty, /colspan="7"/);
+});
+
 test('details preserve full content, escape HTML and unsafe links, and never mark read', () => {
   const { table, cache_calls } = harness();
   assert.match(table, /<template id="aksrt-msg-detail-8">/);