[ljchang]

Supersedes the unpublished v0.8.31 draft. Carries #90, #93, #94:

• Windows first launch fixed — runtime lock recompiled --universal; uvloop no longer pinned on Windows.
• macOS first launch fixed on Macs without Homebrew libomp — sidecar points dyld's fallback path at torch's bundled libomp (found by the new smoke test).
• Windows force-quit no longer orphans the sidecar — kill-on-close Job Object + parent-handle watchdog.
• No console windows during install / launch on Windows.
• Post-release smoke test now installs and first-runs the real artifacts on macOS and Windows runners.