[CI][Test-infra] dev-up test stub server can outlive TERM on Linux/macOS: server.close never completes with open connections

[Chris0Jeky]

Follow-up from PR #2112's EBUSY teardown fix (deliberately left out of that PR because it changes behavior only on lanes that are currently green and could not be verified from the Windows box).

stopWithServer in scripts/ci/dev-up.test.mjs's helperSource calls server.close(cb), whose callback never fires while a connection is open. On Windows this is inert (the SIGTERM handler does not run — measured under Git Bash in the #2112 investigation), but on the Linux/macOS lanes a stub can outlive TERM indefinitely. Fix direction: server.closeAllConnections() before/with close.

Acceptance: stub exits promptly on TERM on all three platforms; the dev-up test file stays green on every lane.

Refs #2111 #2112

[Chris0Jeky]

Implemented in PR #2548 (head 6c10850e6). The synthetic Node HTTP servers now call server.close() first and server.closeAllConnections() immediately after, so accepted connections cannot hold signal teardown indefinitely. The test suite asserts that ordering on every platform and adds a live open-socket TERM regression on Linux/macOS; Windows retains the static contract because native Node signal delivery bypasses the JavaScript listener in Git Bash.

Local evidence: syntax check and the focused lifecycle/static test passed (1/1). The full local suite reached 75 passing tests; its unrelated Bash-on-Windows instability produced 3 failures and 4 cancellations before the existing 9-minute watchdog. PowerShell cases passed. Hosted POSIX/live matrix remains required.

[Chris0Jeky]

Completed by merged PRs #2548 and #2556.

• test: close active dev-up stub connections on signal #2548 fixed the synthetic server teardown contract with closeAllConnections() and added the live POSIX open-socket TERM regression.
• test(ci): allow slow Windows shell output drain #2556 isolated the intentionally slow Windows high-volume stdout/stderr test with a test-only 60-second timeout and a 10-second fixture readiness budget; the production default remains unchanged.
• Hosted required checks for both PRs are green, including the Windows and POSIX lanes.

The original acceptance (prompt TERM exit across supported platforms and a green dev-up test file) is satisfied.