Merge 861d8c6ae23078660aaf9367d2a390b5222824f6 into 9a58616c1e00305f083fe6a9ca5af858dc6d15ab

We fix the core:compile failure by removing the locally-defined ModelContext, ModelContextTool, and DocumentWithModelContext interfaces, which conflicted with the global Document.modelContext augmentation already provided by @mcp-b/webmcp-types. Using document.modelContext directly (now properly typed by the library as ModelContextCore) eliminates the TS2430 error and aligns the inputSchema parsing with the official type (string | undefined rather than string | Record<string, unknown>).