tauri-cli's get_binaries() adds every file in src-tauri/src/bin/ as a
bundle binary, and the deb/rpm packagers copy each one to /usr/bin, so
the dev-only bindings generator ended up as /usr/bin/frontend-contract
(1.0 MB) in release packages and broke downstream repackaging (Copr:
"Installed but unpackaged file(s) found"). There is no bundler option
to exclude a binary, so move the generator to an example target, which
cargo keeps dev-only and get_binaries() never scans, and invoke it via
'cargo run --example'.
Ref https://github.com/clash-verge-rev/clash-verge-rev/pull/8131#issuecomment-6137907930
