Doc Coverage

[bh2smith]

Bring Doc Coverage up to 100% from 59.

See here: https://docs.rs/crate/duners/latest

Generate report with

cargo +nightly rustdoc -Z unstable-options -- -Z unstable-options --show-coverage 

[cursor]

PR Summary

Low Risk
Mostly documentation and CI changes; the only execution risk is potential CI flakiness due to relying on nightly rustdoc coverage output parsing.

Overview
This PR adds a new CI gate that runs cargo +nightly rustdoc --show-coverage and fails PRs if documented/example coverage drops below a checked-in baseline, via a new doc-coverage GitHub Actions job and scripts/check-doc-coverage.sh.

It also bumps the crate version to 0.0.7 and expands Rustdoc across the public API (client, response, parse_utils, parameters, error) with module/field docs and runnable examples to improve docs.rs coverage.

^{Written by Cursor Bugbot for commit a2e9ebb. Configure here.}