Clear session locks on forced delete

[GreyforgeLabs]

Summary

• Refuse normal cortex delete when the resolved session is locked, pointing users to cortex lock remove or --force.
• After a successful forced delete, remove matching entries from session_locks.json so cortex lock list does not retain stale rows.
• Add a CLI regression that imports a session, locks it, force-deletes it, and verifies the lock list is empty.

Fixes PlatformNetwork/bounty-challenge#53210.

Validation

• cargo test -p cortex-cli --test delete_locks --no-default-features --features cortex-tui -- --nocapture
• cargo check -p cortex-cli --no-default-features --features cortex-tui
• cargo fmt --package cortex-cli --check
• git diff --check

[greptile-apps]

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