feat: add built-in Vue plugin

[GRAMMAC1]

Summary

• Add a built-in Vue diagnosis plugin for frontend failure analysis.
• Detect Vue SFC/compiler, Vue runtime, Vue Router, Pinia, Nuxt, hydration, and Vite Vue plugin failure signals.
• Register the Vue plugin in the default diagnosis pipeline after TypeScript and React.
• Add focused tests for Vue ecosystem failures while keeping pure vue-tsc type errors under the TypeScript plugin.

Validation

• pnpm verify

Note: the first sandboxed pnpm verify run passed check/lint/typecheck/tests but failed at the MCP harness step because tsx could not create its IPC pipe under the sandbox. The non-sandbox rerun passed fully, including MCP harness.