[codex] Harden tool continuation history

[HisenWeb]

Summary

• Adds a narrow codex_chat_history helper module for tool-continuation validation.
• Detects duplicate tool outputs before history repair.
• Validates requested tool output call IDs against the selected stored response.
• Validates repaired Chat history before sending it upstream.
• Converts history replay failures into Responses-compatible failed responses instead of forwarding invalid Chat history to OpenCode Go.
• Adds regression tests for matching, unknown, duplicate, orphan, and valid tool-history cases.

Scope

This is behavior-level hardening. It does not copy cc-switch codex_chat_history.rs one-to-one and does not introduce provider registry/session platform logic.

Validation

Not run locally in this connector environment. Recommended:

cargo fmt --check
cargo test --lib
cargo test --test state_store
cargo test --test codex_chat_history_hardening
cargo test

[chatgpt-codex-connector]

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