fix: 修复 esc 转义 > 误写为 " + Excel 表头键取全行并集，新增 11 个单测

tests/webview-escape.test.ts

@@ -0,0 +1,24 @@
+import * as assert from 'assert';
+import { esc } from '../src/panel/webview';
+
+suite('Webview Escape Tests', () => {
+  test('escapes greater-than as >', () => {
+    assert.strictEqual(esc('a > b'), 'a > b');
+    assert.strictEqual(esc('=> x'), '=> x');
+  });
+
+  test('escapes less-than, ampersand and double quote', () => {
+    assert.strictEqual(esc('a < b'), 'a &lt; b');
+    assert.strictEqual(esc('a & b'), 'a &amp; b');
+    assert.strictEqual(esc('say "hi"'), 'say &quot;hi&quot;');
+  });
+
+  test('escapes combined diagnostic message content', () => {
+    const msg = 'Expected === but saw == (a > b && c < d)';
+    assert.strictEqual(esc(msg), 'Expected === but saw == (a &gt; b &amp;&amp; c &lt; d)');
+  });
+
+  test('does not double-escape existing entities', () => {
+    assert.strictEqual(esc('&amp;'), '&amp;amp;');
+  });
+});