Resolve dotted config get keys

[GreyforgeLabs]

Summary

• Resolve cortex config get keys by exact root key first, then by dot-separated TOML table traversal.
• Preserve existing behavior for literal root keys while allowing nested values like model.default.
• Add a CLI regression test for reading [model] default = ... via config get model.default.

Fixes PlatformNetwork/bounty-challenge#46835.

Validation

• cargo test -p cortex-cli --test config_get --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]

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