el-ui vessels are El. The Rust bootstrap implementations were added as
a stopgap but don't belong here — everything should be El source.
Each vessel's src/main.el and manifest.el are the source of truth.
All package management is through manifest.el / epm. Cargo.toml files
were incorrectly added to vessels and the root. Removed root workspace
Cargo.toml + Cargo.lock and all vessel-level Cargo.toml files.
el-graph and el-html were already correct (no Cargo.toml).