feat(pm): expose embeddable command library

[elrrrrrrr]

Summary

• add an utoo-pm library target and reduce the native binary to a thin wrapper
• expose typed command modules matching the native CLI, plus shared initialization, types, version, and clap command metadata
• route CLI dispatch through the public command facade so embedded and native behavior stay aligned
• add an external-crate API test covering every CLI business command

Scope

The public layer is intentionally thin: existing cmd entry points are wrapped while service, helper, and other implementation modules remain private. Process-wide configuration keeps its current first-write-wins semantics.

Validation

• cargo check -p utoo-pm --all-targets --locked
• cargo test -p utoo-pm --test library_api --locked
• cargo clippy -p utoo-pm --all-targets --locked -- --deny warnings
• RUSTDOCFLAGS="-D warnings" cargo doc -p utoo-pm --no-deps --locked
• cargo run -p utoo-pm --bin utoo --locked -- --version
• cargo run -p utoo-pm --bin utoo --locked -- --help
• library suite: 369 passed and 3 ignored; one timing-sensitive auto-update timeout assertion failed on the initial full run and passed when rerun in isolation