fix(cli): use working directory in cd help

[OnlyYu1996]

Fixes PlatformNetwork/bounty-challenge#53091.

Changes:

• Updates the --cd help text to say working directory instead of working root.
• Adds a regression test that renders long help and checks the corrected wording.
• Fixes a stale test import so the cortex-cli test target builds on current main.

Validation:

• cargo +stable fmt --package cortex-cli --check
• cargo +stable test --package cortex-cli cli::args::tests::test_cd_help_uses_working_directory -- --nocapture
• cargo +stable check --package cortex-cli --lib
• git diff --check

[greptile-apps]

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