LSP: Support tsserver request forwarding for Volar v3

Summary

The Claude Code LSP client cannot run Volar v3 (@vue/language-server@3.x) because v3 requires tsserver request forwarding — a mechanism where the Vue language server delegates TypeScript operations to a separate tsserver process. In VS Code, the Volar extension coordinates this by forwarding TS requests between the Vue LSP and VS Code's built-in TypeScript extension.

Claude Code's LSP integration is a simple stdio client with no support for brokering requests between multiple language servers. This forces the vue-volar plugin to pin to Volar v2, which has known issues with Vue 2.7 template type inference (e.g., Options API component bindings resolving to {}).

Impact

• Vue .vue files produce false-positive diagnostics that don't appear in VS Code
• Plugin authors cannot upgrade to Volar v3, which resolved these issues
• The hybridMode: false workaround used by the plugin is not supported in v3

Expected behavior

Claude Code's LSP client should support request forwarding (or an equivalent mechanism) so that language servers like Volar v3 can delegate TypeScript operations to a tsserver sidecar process.

Environment

• Claude Code on Windows 11 (Git Bash)
• vue-language-server@2.2.12 (v3 incompatible)
• @vue/language-core@3.0.8 available in project but unusable