cli: Kill the serve-web process tree on idle timeout

[Kie (Kidsunbo)]

Fixes #332764

serve-web previously killed only the direct launcher process when reaching
the idle timeout, potentially leaving the Node.js server and its descendants
running.

Use kill_tree to terminate the complete process tree, wait for the launcher
to exit, and fall back to a forced kill after a timeout.

[Kie (Kidsunbo)]

Kie (Kie (@Kidsunbo)) please read the following Contributor License Agreement(CLA). If you agree with the CLA, please reply with the following information.

@microsoft-github-policy-service agree [company="{your company}"]

Options:

• (default - no company specified) I have sole ownership of intellectual property rights to my Submissions and I am not making Submissions in the course of work for my employer.

@microsoft-github-policy-service agree

• (when company given) I am making Submissions in the course of work for my employer (or my employer has intellectual property rights in my Submissions by contract or applicable law). I have permission from my employer to make Submissions and enter into this Agreement on behalf of my employer. By signing below, the defined term “You” includes me and my employer.

@microsoft-github-policy-service agree company="Microsoft"

Contributor License Agreement

@microsoft-github-policy-service agree

[Copilot]

Pull request overview

Updates serve-web idle-timeout shutdown to reduce orphaned server processes.

Changes:

• Uses kill_tree for process-tree termination.
• Waits five seconds before attempting a forced kill.

Suppressed comments (1)

cli/src/commands/serve_web.rs:947

• kill_tree only sends SIGTERM, but this timeout waits for the launcher alone. If the shell exits while a descendant ignores or hangs on SIGTERM, child.wait() succeeds immediately and the forced-kill path is skipped; even on timeout, child.kill() targets only the launcher. The shutdown can therefore still leave server-main.js running. The fallback needs to force-kill the captured process tree/process group (and verify descendants exit), not just the direct child.

					if tokio::time::timeout(REAP_TIMEOUT, child.wait()).await.is_err() {

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.

[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.

Suppressed comments (1)

cli/src/commands/serve_web.rs:947

• The timeout only waits for the launcher, not the descendants that kill_tree signaled. Because the shell can exit immediately while server-main.js is still shutting down or ignores SIGTERM, child.wait() can succeed before the five seconds elapse; the fallback is then skipped. Even when the timeout does fire, child.kill() force-kills only that launcher, recreating the orphan scenario this change is intended to prevent. The graceful tree operation needs to retain/observe the descendant set and force-kill the whole tree after the grace period, rather than keying escalation solely on the launcher's exit.

					if tokio::time::timeout(REAP_TIMEOUT, child.wait()).await.is_err() {