[app-server] fix config loading for conversations

[celia-oai]

Currently we don't load config properly for app server conversations. see: https://linear.app/openai/issue/CODEX-3956/config-flags-not-respected-in-codex-app-server. This PR fixes that by respecting the config passed in.

Tested by running cargo build -p codex-cli && RUST_LOG=codex_app_server=debug CODEX_BIN=target/debug/codex cargo run -p codex-app-server-test-client -- \ --config model_providers.mock_provider.base_url=\"http://localhost:4010/v2\" \ --config model_provider=\"mock_provider\" \ --config model_providers.mock_provider.name="hello" \ send-message-v2 "hello"
and verified that the mock_provider is called instead of default provider.

#closes https://linear.app/openai/issue/CODEX-3956/config-flags-not-respected-in-codex-app-server

[owenlin0]

approving to get --config flags working for app-server, but +1 to unifying config code / making it easier to follow

[owenlin0]

btw the fix ultimately was that we never read &self.cli_overrides from codex_message_processor? nice find!

[celia-oai]

btw the fix ultimately was that we never read &self.cli_overrides from codex_message_processor? nice find!

yup yup! I agree it's confusing because cli_overrides is an overloaded term and easy to miss when we are not passing in all the overrides. will rename first to make it clearer

[bolinfest]

I think some terminology needs to be tightened up here. The things that are currently called harness_overrides are not defined by the harness but a NewConversationParams, so I think some other name is in order.

[jif-oai]

Lots of changes on this recently so I rely on @.bolinfest for this

[bolinfest]

ok, let's go with the typesafe_overrides thing and this is good by me: thanks for fixing!