fix(ai): route Codex fingerprint convergence through ai_serving transport facade

[JinPengGeng]

Problem

Current main@f3a12c10080cff724fa0b58fb196f4c6e40c409b fails the existing gateway architecture test:

tests::architecture::ai_serving::ai_serving_routes_provider_transport_deps_through_facade

The failure reports:

apps/aether-gateway/src/ai_serving/planner/decision_input.rs
-> crate::provider_transport

Commit 8cf381b0c3b6fd485ec4b4333c30fe5b251325b3 added a direct runtime call to crate::provider_transport::apply_codex_oauth_fingerprint_convergence. The established boundary requires provider-transport dependencies to go through apps/aether-gateway/src/ai_serving/transport.rs.

Reproduction

cargo nextest run -p aether-gateway --lib

Observed in downstream CI: https://github.com/JinPengGeng/aeris-token/actions/runs/31703155005

Expected fix

Re-export apply_codex_oauth_fingerprint_convergence from ai_serving/transport.rs and call it through the AI-serving transport facade, or intentionally revise the architecture contract if the boundary has changed.