refactor: rename engine/, services/, util/ directories by domain

[magnus-madsen]

Summary

• Reorganize remaining grab-bag directories into domain-specific modules:
  • engine/ -> protocol/ (request types enum, status codes)
  • services/{releases,state} + util/ensureFlixExists -> compiler/ (download, releases, version state)
  • services/{flixLspTerminal,releaseVirtualDocument} + util/{userMessages,showStartupProgress} -> ui/
  • util/createLanguageClient -> lsp/clientFactory
  • services/eventEmitter -> util/eventBus
  • services/timers -> util/timers
• Delete engine/ and services/ directories entirely
• All files renamed to more meaningful names (e.g. jobs.ts -> requests.ts, state.ts -> installedVersion.ts)

Final structure

client/src/
├── extension.ts
├── commands/          — user-facing command handlers
├── compiler/          — Flix compiler download, releases, version state
├── lsp/               — LSP client, session, watchers, notifications
├── protocol/          — request types and status codes
├── repl/              — REPL lifecycle and JVM args
├── ui/                — terminal, messages, progress, release notes
└── util/              — event bus, timers

Test plan

• tsc --noEmit passes (client)
• npm run build passes (esbuild bundle)
• prettier --check passes
• Git detects all moves as renames (history preserved)
• Existing integration tests pass (npm test)

🤖 Generated with Claude Code