[CI] Add list_pages_and_boards MCP tool

[egdev6]

Summary

Add an MCP tool that lists the pages of the current Penpot file and their top-level boards with stable metadata so AI workflows can navigate the document without falling back to ad hoc scripting.

Scope

• expose pages from the current file
• expose top-level boards per page
• include id, name, type, bounds, visible, locked, and childCount
• support optional filtering by pageName

Acceptance Criteria

• returns all pages correctly
• returns top-level boards for each page correctly
• supports page filtering
• output is usable by AI workflows without manual execute_code discovery

Tasks

• implement ListPagesBoardsTool.ts
• define input/output schema
• read pages from the current file
• extract top-level boards from each page
• include required metadata fields
• register the tool in PenpotMcpServer.ts
• add tests with a bridge mock
• document usage examples

Additional notes

This is the navigation primitive for the rest of the Penpot design-system workflow.