chore: Trim unused dependency features for faster compilation (#12094)
## Summary
Trims unused default features from four workspace dependencies to reduce
compilation overhead:
- **`async-graphql`**: Disables `playground`, `email-validator`,
`tempfile` defaults — only `graphiql` is used (via `GraphiQLSource`).
Removes `fast_chemail` and `ascii_utils` from the dep tree
- **`nix`**: Centralizes as a workspace dep with `default-features =
false`. `turborepo-process` declared all 30+ features but only uses
`sys::termios` (`term`). `turborepo-ui` only uses `sys::signal`. Removes
`memoffset 0.7.1` from the dep tree. **0.95s saved**
- **`petgraph`**: Disables `graphmap`, `matrix_graph`, `stable_graph`
defaults — only `Graph`/`DiGraph`/`NodeIndex` and algo/visit traits are
used
- **`chrono`**: Disables `oldtime`, `js-sys`, `wasm-bindgen`,
`android-tzdata`, `windows-targets` defaults — only `DateTime`, `Local`,
`Utc`, `Duration` are used. **0.41s saved**
Zero code changes — only Cargo.toml feature declarations. 5 compilation
units removed.