fix(cli): document multiple lock session ids

[felipegr0ssi]

Summary

• document multi-session usage in cortex lock --help
• update the no-argument lock guidance to show add/remove with multiple IDs
• add parser/help coverage for multiple session IDs

Bounty issue: PlatformNetwork/bounty-challenge#53214

Testing

• git diff --check

Note: I could not run the Rust test suite in this Windows environment because cargo, rustc, and rustfmt are not installed.

[greptile-apps]

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