Filter logs clear to log files

[GreyforgeLabs]

Summary

• Add shared log-file detection for log cleanup.
• Restrict cortex logs --clear deletion to .log and .txt files.
• Add CLI regression coverage that non-log sidecar files remain after cleanup.

Fixes PlatformNetwork/bounty-challenge#51691.

Validation

• cargo test -p cortex-cli --test logs_clear --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
• git diff --cached --check

[greptile-apps]

Your free trial has ended. If you'd like to continue receiving code reviews, you can add a payment method here.