GeezerVison

Summary

• Replace the WASI job's installer with the official Wasmer 7.5.0 Linux x86_64 archive, pinned by SHA256.
• Retry transient download failures, fail on HTTP errors or checksum mismatch, and run wasmer --version before exporting the runtime and starting the Rust build.
• Keep this restricted to the existing ubuntu-latest WASI job, explicitly rejecting unexpected platforms. No new jobs or test suppression.

Why

The existing installer returned exit 0 after File download failed with code 500 in #9745's WASI job. Setup was marked successful, an expensive build ran, and the first snippet failed with wasmer: command not found (127). A previous run exhibited the same pattern with HTTP 504. The setup action retries downloading its installer, not the runtime download inside it.

The checksum matches the digest of the official v7.5.0 release. Using a fixed GitHub release avoids the mutable installer/download redirect while preserving retries for transient release-host failures.

Validation

• Executed the exact workflow shell block locally against the official release: SHA256 OK, wasmer 7.5.0, environment/path export succeeded.
• Fault injection: download error, checksum mismatch, and missing executable all fail before exporting PATH/environment (exit 22, 1, and 127 respectively).
• actionlint passed; normal commit hooks passed; zizmor reports the same four existing low-severity self-repository findings, no new findings.
• No interpreter changes; workspace/CAPI tests and full WASI build were not repeated locally for this workflow-only patch. CI is the remaining hosted-run validation.

Independent change based on current main, not stacked on the WASI coverage or pytest PRs. No Actions rerun was requested.

AI assistance: OpenAI Codex (model version unavailable).