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.

Mark all source files with a comment indicating they are not optimized
for documentation purposes.

Add convenience presets (`mini`, `advanced`, `full`, `build_advanced`,
`build_full`) to `mingling/Cargo.toml` and document them in both
English and Chinese feature docs. Update getting-started guides to
reflect the new default `core`/`macros` features.

Update all references across docs, examples, and configuration files to
use the shorter `extras` feature name.

Add `docs_rs` feature flag to enable docs.rs-specific configuration,
including `--generate-link-to-definition` and logo display.

Include the feature in build scripts, editor settings, and feature
constants for consistent documentation generation.

formatting

Add `MINGLING_CORE` and `MINGLING_MACROS` feature flag constants to
the mingling crate, mirroring existing pattern for other features

Reorganize imports and reformat closures in mingling_picker for
consistent style