Improve robustness of FwLiteWeb shutdown handlers

[Copilot]

Addresses open CodeRabbit suggestions for graceful shutdown implementation between Paratext and FwLiteWeb process.

C# stdin listener (Program.cs)

• Handle EOF to prevent infinite loop when parent process dies
• Accept case-insensitive "shutdown" command with whitespace tolerance

string? line;
while ((line = await Console.In.ReadLineAsync()) is not null
       && !string.Equals(line.Trim(), "shutdown", StringComparison.OrdinalIgnoreCase))
{ /* keep waiting */ }

TypeScript shutdown function (main.ts)

• Clear kill timer on exit/error to prevent resource leak
• Check exitCode !== null for idempotency if process already terminated
• Guard stdin writes with null checks and try-catch for destroyed streams
• Coordinate forced kill with flag to resolve Promise correctly

// Already exited?
if (fwLiteProcess.exitCode !== null) {
  resolve(fwLiteProcess.exitCode === 0);
  return;
}

let forced = false;
const killTimer = setTimeout(() => {
  forced = true;
  fwLiteProcess.kill('SIGKILL');
}, 10000);

fwLiteProcess.once('exit', (code, signal) => {
  clearTimeout(killTimer);
  resolve(code === 0 || forced);
});

---

💬 We'd love your input! Share your thoughts on Copilot coding agent in our 2 minute survey.

[coderabbitai]

Important

Review skipped

Bot user detected.

To trigger a single review, invoke the @coderabbitai review command.

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

---

_{Comment @coderabbitai help to get the list of available commands and usage tips.}