Upgrade Rsdoctor to v2

Upgrade with the smallest behavior-preserving diff. Treat the official migration guides and the installed package exports as the source of truth:

• https://rsdoctor.rs/guide/start/migration-v2
• https://rsdoctor.rs/config/options/options-v2

Workflow

1. Audit the current integration
   • Read package.json, the lockfile, Node.js version files, and the build scripts.
   • Determine the installed Rsdoctor package versions from the lockfile or package metadata, and check which package provides the active RsdoctorRspackPlugin. Migrate a 1.x @rsdoctor/rspack-plugin integration, including any partially migrated setup that still imports it. If @rsdoctor/core 2.x already provides the active plugin, validate the integration instead of migrating it again. @rsdoctor/core alone does not prove a 2.x integration because 1.x projects may use it for custom rules. Distinguish direct integration from framework-owned transitive 1.x dependencies.
   • Locate Rspack, Rsbuild, and Rsdoctor configuration files. Preserve any environment condition that enables Rsdoctor only for selected builds.
   • Search source, scripts, and editor configuration for @rsdoctor/, RsdoctorRspackPlugin, legacy options, MCP setup, and report-output assumptions.
   • Record the current build command and expected report formats before editing.