The Windows Hub companion installers are promoted to the main OpenClaw
release via a manual workflow_dispatch, not every release includes them.
The /releases/latest/download/ links resolved to v2026.6.6 which does not
have the OpenClawCompanion assets, causing 404 errors.
Pin the links to v2026.6.5 (the latest release that has the assets) and
add a fallback note directing users to the releases page when a release
is missing the companion installers.
Fixes#92470