feat: add capture_screenshot tool

[vrecluse]

Summary

• add a clean capture_screenshot MCP tool ported onto current main
• use an in-project wrapper scene to capture the active Godot viewport without Windows screen capture APIs
• add a regression test for tool exposure and document the new tool

Context

This replaces the stale implementation in #51 with a conflict-resolved branch based on current main.

Test Plan

• npm run build
• npm test
• run a real Godot project and verify capture_screenshot returns a PNG payload

[vrecluse]

@Coding-Solo I just resolved the merge conflicts and pushed the updated branch. This feature is genuinely important for the Godot MCP workflow because screenshot capture closes a major gap in the agent feedback loop: without it, tools can only rely on logs, while with it they can inspect the actual running viewport for visual debugging and iteration. Local verification is still good after the update (
pm test and
pm run build both pass). When you have a chance, please take another look and merge this soon if it looks good.