First tagged release of the revenexx fork.

Tracks upstream open-runtimes/executor 0.25.3 + the fork's host.docker.internal patch (see FORK.md).

Includes the upstream build-failure surfacing (dedicated BUILD_FAILED, real build log instead of "Internal server error.") and the aligned build-cache protocol (build-cache-{env,restore,save}.sh). CI green (Build + E2E).

→ ghcr.io/revenexx/platform-runtimes-executor:0.25.3-rvnxx.1