feat: browser_choose_file (#52)

Resolves https://github.com/microsoft/playwright-mcp/issues/31.

Prompt used for testing: 
```
upload test.txt to dropbox
```

This won't work for asynchronously opened filechoosers, but let's start
with the synchronous variant. I also tested with including the file
chooser open state in the snapshot, but that didn't give better results.

I also tested with OneDrive and WeTransfer, but somehow our ARIA
snapshots for those pages are missing some elements that are crucial to
locate the upload buttons.

src/tools/utils.ts

@@ -73,23 +73,36 @@ async function waitForCompletion<R>(page: playwright.Page, callback: () => Promi
 
 export async function runAndWait(context: Context, status: string, callback: (page: playwright.Page) => Promise<any>, snapshot: boolean = false): Promise<ToolResult> {
   const page = context.existingPage();
+  const dismissFileChooser = context.hasFileChooser();
   await waitForCompletion(page, () => callback(page));
-  return snapshot ? captureAriaSnapshot(context, status) : {
+  if (dismissFileChooser)
+    context.clearFileChooser();
+  const result: ToolResult = snapshot ? await captureAriaSnapshot(context, status) : {
     content: [{ type: 'text', text: status }],
   };
+  return result;
 }
 
 export async function captureAriaSnapshot(context: Context, status: string = ''): Promise<ToolResult> {
   const page = context.existingPage();
+  const lines = [];
+  if (status)
+    lines.push(`${status}`);
+  lines.push(
+      '',
+      `- Page URL: ${page.url()}`,
+      `- Page Title: ${await page.title()}`
+  );
+  if (context.hasFileChooser())
+    lines.push(`- There is a file chooser visible that requires browser_choose_file to be called`);
+  lines.push(
+      `- Page Snapshot`,
+      '```yaml',
+      await context.allFramesSnapshot(),
+      '```',
+      ''
+  );
   return {
-    content: [{ type: 'text', text: `${status ? `${status}\n` : ''}
-- Page URL: ${page.url()}
-- Page Title: ${await page.title()}
-- Page Snapshot
-\`\`\`yaml
-${await context.allFramesSnapshot()}
-\`\`\`
-`
-    }],
+    content: [{ type: 'text', text: lines.join('\n') }],
   };
 }