chore: upgrade to Rust 1.92.0

[viyatb-oai]

Summary

• Upgrade Rust toolchain used by CI to 1.92.0.
• Address new clippy derivable_impls warnings by deriving Default for enums across protocol, core, backend openapi models, and windows-sandbox setup.
• Tidy up related test/config behavior (originator header handling, env override cleanup) and remove a now-unused assignment in TUI/TUI2 render layout.

Testing

• just fmt
• just fix -p codex-tui
• just fix -p codex-tui2
• just fix -p codex-windows-sandbox
• cargo test -p codex-tui
• cargo test -p codex-tui2
• cargo test -p codex-windows-sandbox
• cargo test -p codex-core --test all
• cargo test -p codex-app-server --test all
• cargo test -p codex-mcp-server --test all
• cargo test --all-features

[joshka-oai]

General approval - unsure what the mentioned changes are about here. Can you revert these and check the errors?