Add `#![deny(missing_docs)]` across multiple crates and fill in
documentation for all public items, including struct fields, enum
variants, trait methods, and proc macros.  Also mark two shell scripts
as executable.

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.

Use `--manifest-path mingling/Cargo.toml` instead of `--workspace` to
avoid generating documentation for unintended root workspace crates

Add a helper script `.run/src/bin/cov-test.rs` that generates
HTML coverage reports using `cargo llvm-cov` and moves the
output files to the `docs/cov-test/` directory

unhide logic