test(web): resolve the Discussion CSS guard path from the test file

The guard read the component through process.cwd(), which is the repo root
under the sharded root test run, so the file was missing in CI. Resolve it
from import.meta.dirname like the neighbouring panel test.

Author: elkaix

apps/pythinker-web/test/expert-opinion-session.test.ts

@@ -1,5 +1,5 @@
 import { readFileSync } from 'node:fs';
-import { resolve } from 'node:path';
+import { join } from 'node:path';
 
 import { mount } from '@vue/test-utils';
 import { defineComponent } from 'vue';
@@ -250,7 +250,7 @@ describe('Expert Talk session transcript', () => {
 
 describe('Expert Talk exchange scrolling', () => {
   it('lets a wheel over a reasoning box chain to the transcript scroller', () => {
-    const source = readFileSync(resolve(process.cwd(), 'src/components/chat/ExpertTalkExchange.vue'), 'utf8');
+    const source = readFileSync(join(import.meta.dirname, '../src/components/chat/ExpertTalkExchange.vue'), 'utf8');
     const thinkingRule = source.slice(source.indexOf('.expert-talk__thinking {'));
     const block = thinkingRule.slice(0, thinkingRule.indexOf('}'));
     expect(block).toContain('overflow: auto');