Reuse exec conversation ID for tool calls

[GreyforgeLabs]

Summary

• Pass the exec session conversation ID into each tool call execution
• Build tool contexts with the session ID instead of generating a fresh ID per call
• Add a regression test for tool context conversation ID propagation

Validation

• cargo fmt --package cortex-exec --check
• git diff --check
• cargo test -p cortex-exec
• cargo check -p cortex-exec

Addresses PlatformNetwork/bounty-challenge#53130.

[greptile-apps]

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