Move CI, dev tools, and configs from root-level scattered locations into
a
unified `dev/` directory structure. Update all references across build
scripts, documentation, and editor configurations.

Also consolidate editor config generation into build.rs for automated
synchronization of rust-analyzer settings across VS Code and Zed.

BREAKING CHANGE: Replace the `build`/`builds` feature system with
compile-time macro-driven generation. `gen_program!()` now automatically
invokes `build_comp!()` and `build_pathf!()` when the `comp`/`pathf`
features are enabled, eliminating the need for `build.rs` and
`[build-dependencies]` blocks.

This removes the `build` feature, the `mingling::build` module, and all
related build-time API functions. Completion scripts are now written to
`{target_directory}/mingling/` instead of `target/release/`. The
`mingling_cli` uses `build_comp!("mling")` for its custom binary name.

The legacy `parser` feature and its module tree (`mingling::parser`,
`Argument`, `Picker`, `Pickable`, etc.) have been fully removed and
replaced by the `picker` feature powered by `arg-picker`.

BREAKING CHANGE: Remove `parser` feature and use `picker` instead.
Migration guide: Replace `features = ["parser"]` with
`features = ["picker"]` and update API usage per the provided table.

Introduce `might_be_async` as a workspace dependency, add it to
`mingling_core`, and regenerate all Cargo.lock files accordingly.
Multiple examples and test packages also pick up a newly transitive
`equivalent` crate.

Add a root package `mingling-workspace` with an empty `main.rs` to
improve Cargo workspace compatibility.