fix: handle agent filter wildcard

[Bortlesboat]

Summary

• handle a single * agent filter as a match-all glob before slicing wildcard patterns
• add a CLI integration regression for cortex agent list --filter '*' --json

Related to PlatformNetwork/bounty-challenge#45640.

Tests

• cargo test -p cortex-cli --test agent_filter agent_list_single_wildcard_filter_does_not_panic -- --nocapture
• cargo check -p cortex-cli
• cargo fmt --check --package cortex-cli
• git diff --check

[greptile-apps]

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