Add Claude Code LSP support

[Copilot]

Claude Code supports LSP through plugins. This extends gh-aw’s experimental lsp configuration to the Claude engine.

Changes

• Claude integration

  • Generates a temporary .lsp.json plugin.
  • Loads it with --plugin-dir.
  • Adds LSP to Claude’s tool allowlist.

• Language-server setup

  • Reuses existing pinned installation and runtime detection.
  • Translates fileExtensions to Claude’s extensionToLanguage format.

• Validation

  • Allows lsp with Copilot and Claude.
  • Rejects Claude bare mode, which disables plugins and LSP.

• Documentation

  • Updates schema and engine capability references.

engine: claude

lsp:
  go:
    command: gopls
    fileExtensions:
      ".go": go