Summary

The asset naming carried Burrito-era baggage: the binary is named anvil, not anvil-runner, so asset filenames like anvil_runner_linux_amd64_2026.04.1 had an unnecessary _runner infix that confused everything downstream (install script, controller regex, service files).

Rename:

• anvil_runner_linux_amd64_X.Y.Z → anvil_linux_amd64_X.Y.Z
• anvil_runner_linux_arm64_X.Y.Z → anvil_linux_arm64_X.Y.Z

CI artifact names (unversioned, in .anvil.yml) are renamed to match.

Coordinate with fangorn/anvil PR #49

That PR updates the server’s /runner/download controller to find assets by the new name pattern. Merge this PR first so a new CalVer release is published with the new names before the server PR is deployed. Between the merges the server will return 404 for /runner/download briefly — keep the gap short.

Test plan

• cargo fmt --check, cargo clippy -- -D warnings, cargo test all pass locally
• CI publishes a new release (2026.04.3 or later) with anvil_linux_amd64_* asset names

Refs #1