Replace the ZIP-based template archive workflow with direct
directory copying. Delete the `package-mling-tmpls` tool and
remove the `zip` dependency.

Update install scripts to build from manifest and copy binaries
manually instead of using `cargo install`. Add load scripts for
bash, zsh, fish, and PowerShell to set up PATH and source
completion scripts from external packages.

script executable

`arg-picker` is excluded from the workspace test command and tested
on its own due to conflicting `mingling_support` feature doctests.
Also remove unused `mling/res` ignore directories.

Use `--workspace` for build, clippy, and test tasks to cover
feature-gated code instead of relying on default features. Skip
workspace members in individual crate tasks to avoid redundant runs.

Add the Arborium JS library header to the documentation build via
RUSTDOCFLAGS and docs.rs metadata so generated docs include the
interactive Arborium components.

Add module-level docs for the build module via include_str and
restrict public re-exports to explicit items instead of glob imports.