Fix desktop app not opening / engine not starting (v1.1.1)

[ccharafeddine]

Summary

On Windows, the v1.1.0 .exe does nothing when launched. This PR fixes the two causes.

1. No window, and the process stays running. If the fixed port 47813 fails with any error other than EADDRINUSE, startServer rejects and nothing handles it. On Windows, a port inside a Hyper-V/WSL/Docker reserved range fails with EACCES. The app then creates no window, but the process keeps running and holds the single-instance lock, so every later launch exits silently. Now any listen error falls back to a random port. If startup still fails, the app shows an error box and exits.
2. The engine never started in Electron. BrowserWindow doesn't honor COOP/COEP, so crossOriginIsolated stays false and SharedArrayBuffer is undefined. The multi-threaded engine therefore couldn't start. v1.0.0 never hit this because it was actually running the single-threaded build. The fix is app.commandLine.appendSwitch('enable-features', 'SharedArrayBuffer').

Also in this PR:

• On a second launch, the running app shows and focuses its window, or creates one if none exists.
• The portable .exe now shows a splash screen while it unpacks its ~320MB.
• Version bumped to 1.1.1, with release notes in docs/release-notes/v1.1.1.md.

Testing

• npm run lint, npm test (45 tests) and npm run build pass.
• Reproduced the missing window with a simulated EACCES, then confirmed the fallback port and the error-box path.
• Ran the real Electron app under Xvfb, both in dev and as the packaged linux-unpacked build:
  • the engine runs with 3 threads at about 1M nps;
  • each drag-move gets a best line in about 200ms;
  • with port 47813 already taken, the app falls back to a random port;
  • a second launch hands off to the running app and exits.
• I haven't run it on Windows itself.

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https://claude.ai/code/session_017ZHKbLKcpoa8QJGzqkbDTJ

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