fix(codex): keep delegated child-agent output out of parent chats - #5955

💭 The imports are fine, and this looks like an Effect service change since it modifies makeCodexSessionRuntime and the adapter. I need to check if there are any convention violations—no new errors, Layer.succeed, ManagedRuntime, or runPromise in the changed lines. Looking at the diff, it mostly adds helper functions and logic inside makeCodexSessionRuntime, so I should verify there aren't any new error classes or other violations introduced. The AgentsPanel.tsx file looks fine from a service conventions perspective. I'm also checking the test file and other parts of the diff—CodexAdapter.test.ts uses the right assertion patterns. The removed doc comment about "WIP, probe-gated" was legitimately updated to match the new behavior, so that's not a concern. Everything checks out.