fix(ci): avoid duplicate example builds in test job

[chaliy]

Summary

• stop the CI test job from rebuilding examples during cargo test
• keep doctest coverage by running doc tests in a dedicated step
• leave example coverage in the existing Examples job

Why

main went red on GitHub Actions run 24465694329 for commit e51470a because the Test job exhausted runner disk while linking python_scripts during cargo test --features http_client,ssh.

That job was compiling examples even though examples already have their own dedicated workflow job. Splitting the coverage avoids duplicate example links in the Test job and removes the disk-pressure path that broke main.

Test Plan

• cargo test --workspace --lib --bins --tests --features http_client,ssh --no-run
• cargo test --workspace --doc --features http_client,ssh
• just pre-pr (fails on a pre-existing bash_comparison_tests mismatch in cargo test; unrelated to this workflow-only change)