Add GraphQL LSP server support

[sandiiarov]

Feature Request

Add GraphQL Language Server Protocol (LSP) support to OpenCode to provide IDE-like features for GraphQL projects.

Problem

Currently, OpenCode doesn't have dedicated GraphQL LSP support. While Biome can handle .graphql/.gql files, it only provides linting - not the full LSP experience (autocomplete, hover info, go-to-definition, diagnostics against schema).

Proposed Solution

Add built-in GraphQL LSP server using graphql-language-service-cli (the official GraphQL LSP implementation) to provide:

• Diagnostics for GraphQL syntax linting and validation (spec-compliant)
• Autocomplete suggestions for fields, arguments, types, and variables
• Hover information showing field descriptions
• Go-to-definition for types, inputs, enums, and fragment definitions
• Support for inline GraphQL in JavaScript/TypeScript/Vue/Svelte/Astro files

Technical Details

• LSP Server: graphql-language-service-cli (provides graphql-lsp binary)
• Command: server -m stream (stream mode for LSP stdio communication)
• Extensions: .graphql, .gql (standalone) + .ts, .tsx, .js, .jsx, .vue, .svelte, .astro (inline)
• Detection: Auto-detect via presence of GraphQL config files:
  • .graphqlrc.* (all formats: .yml, .yaml, .json, .js, .cjs, .mjs)
  • graphql.config.* (all formats: .yml, .yaml, .json, .js, .cjs, .mjs)
• Auto-installation: Install graphql-language-service-cli globally via bun if not found
• Coexistence: Works alongside Biome and other LSPs without conflicts

References

• Official GraphQL LSP: https://github.com/graphql/graphiql/tree/main/packages/graphql-language-service-cli
• Similar to existing TailwindCSS LSP support (#9303)