fix: browser test fixes and typecheck script

- Fix widgetTextBox locator in ComfyPage
- Add exact match for 'Add' button in search filter panel
- Fix ClipboardHelper to properly handle undefined vs null locators
- Use canvasOps.dragAndDrop in NodeOperationsHelper
- Use nodeOps.waitForGraphNodes in link interaction tests
- Add typecheck:browser script for browser tests

Amp-Thread-ID: https://ampcode.com/threads/T-019c1696-c595-7724-8dca-64f73f19f478
Co-authored-by: Amp <amp@ampcode.com>

browser_tests/fixtures/components/ComfyNodeSearchBox.ts

@@ -30,7 +30,7 @@ export class ComfyNodeSearchFilterSelectionPanel {
   async addFilter(filterValue: string, filterType: string) {
     await this.selectFilterType(filterType)
     await this.selectFilterValue(filterValue)
-    await this.page.getByRole('button', { name: 'Add' }).click()
+    await this.page.getByRole('button', { name: 'Add', exact: true }).click()
   }
 }