fix: preserve reasoning lineage across interrupted retries

[dzianisv]

Summary

Fix the interrupted-replay bug that leaves history with a function_call but not its required reasoning item, which causes the next /responses request to fail and makes the session unusable.

Closes #47.

Changes

• persist partial reasoning items from response.output_item.added into in-memory history immediately
• upsert completed reasoning items by id so a completed reasoning item replaces its partial predecessor instead of duplicating it
• always attach response item ids on /responses requests so reasoning/function-call lineage survives replay on the standard Responses wire path too
• rebuild retry prompts from live session history before transport retries so same-turn retries include any reasoning/call/output items already recorded before the disconnect
• add regression coverage for both user-interrupt follow-up replay and incomplete-stream retry replay

Testing

• cargo test -p codex-core --lib context_manager::history::tests::record_items_replaces_reasoning_item_with_same_non_empty_id -- --exact
• cargo test -p codex-core --test all suite::abort_tasks::interrupt_tool_records_history_entries -- --exact
• cargo test -p codex-core --test all suite::stream_no_completed::retries_on_early_close -- --exact
• cargo test -p codex-core --test all suite::cli_stream::responses_mode_stream_cli -- --exact

[dzianisv]

Rebased this branch onto the latest main after merging #46 and #51.

Local validation completed:

• cargo test -p codex-core --lib context_manager::history::tests::record_items_replaces_reasoning_item_with_same_non_empty_id -- --exact
• cargo test -p codex-core --test all suite::abort_tasks::interrupt_tool_records_history_entries -- --exact
• cargo test -p codex-core --test all suite::stream_no_completed::retries_on_early_close -- --exact
• cargo test -p codex-core --test all suite::cli_stream::responses_mode_stream_cli -- --exact

Current blockers are fork-wide CI issues rather than branch-local behavior:

• Fix cargo-deny failure for tar RUSTSEC-2026-0068 #44 cargo-deny / tar RUSTSEC-2026-0068
• Fix fork-wide argument-comment lint failures in TUI files #52 argument-comment lint failures in untouched TUI files
• Investigate Bazel macOS SDK fetch 403 in experimental workflow #43 / Fix PR CI runner allocation on dzianisv/codex fork #29 Bazel experimental failures and fork runner allocation issues