fix(mcp): use outputFile for custom filenames to respect --output-dir

[Limitless2023]

Summary

Fixes microsoft/playwright-mcp#1390

When --output-dir is configured, custom filenames passed to screenshot/pdf/etc. tools were being saved to workspace root instead of --output-dir.

Root Cause

In resolveClientFile(), when a suggestedFilename was provided, it used workspaceFile() which always saves to workspace root. Only auto-generated filenames used outputFile() which respects --output-dir.

Fix

Changed resolveClientFile() to always use outputFile() for both auto-generated and custom filenames. The outputFile() method already correctly handles suggestedFilename - it uses it as the basename and resolves against outputDir.

Code Change

- let fileName: string;
- if (template.suggestedFilename)
-   fileName = await this._context.workspaceFile(template.suggestedFilename, this._clientWorkspace);
- else
-   fileName = await this._context.outputFile(template, { origin: 'llm' });
+ const fileName = await this._context.outputFile(template, { origin: 'llm' });