ci: remove release runner Python and sudo assumptions

[cbusillo]

Summary

• remove sudo from the release preflight cargo target-dir preparation so self-hosted runners without sudo can proceed
• remove setup-python from release jobs and use the runner's existing python3 for the rust-toolchain parse

Validation

• ruby -e 'require "yaml"; YAML.load_file(".github/workflows/release.yml"); puts "yaml ok"'
• git diff --check
• rg -n "Setup Python 3.12|setup-python|python-version|sudo mkdir|sudo chown|python -c" .github/workflows/release.yml
• ./build-fast.sh

Refs #87