feat: add React diagnosis plugin

[GRAMMAC1]

Summary

• Add a built-in React diagnosis plugin for common React and Next.js frontend failures.
• Detect and classify hook-rule errors, hydration mismatches, server/client component boundary issues, invalid component rendering, JSX runtime issues, and Next-specific runtime/build signals.
• Register the React plugin between TypeScript and generic fallback analysis.
• Tighten TypeScript plugin detection so React runtime failures with .tsx stack frames are not incorrectly claimed as TypeScript diagnostics.
• Extract shared text helpers used by React and TypeScript plugins.
• Add React plugin tests for invalid hook calls, Next hydration mismatch, and server/client boundary failures.
• Update the benchmark report after diagnosis output changes.

Validation

• pnpm verify
• pre-commit Biome check during commit

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