Upgrade embedded Codex runtime to 0.162.1

[jsgrrchg]

Upgrade the owned Codex ACP runtime from 0.159.0 to the stable 0.162.1 release, keeping the desktop staging baseline and vendored sources aligned with the upstream tag and commit.

Changes

• Update the pinned Codex dependencies and lockfile, and sync the vendored PTY implementation and tests while retaining our Windows compatibility fixes.
• Adapt command completion, turn submission, paginated history, and subagent metadata handling to the updated upstream types.
• Update packaging checks, runtime upgrade smoke fixtures, and baseline/rollback documentation.
• Verify the new fallback default (gpt-6.1-sol) while preserving explicit model selections and the runtime model catalog.

Validation

• All 1,161 tests passed: 176 adapter/host/PTY tests, 370 native backend tests, and 615 desktop/frontend/staging tests.
• Runtime workspace Clippy with warnings denied, Rust formatting, and source-alignment checks passed.
• PTY cross-compilation checks passed for Windows x64 and macOS ARM64.
• Functional smoke checks passed across upgrade, rollback, and re-upgrade using independently built 0.159.0 and 0.162.1 runtimes, including session loading/resume, model selection, paginated history, and missing-host failure handling.

Native Windows/macOS execution, signing, and release packaging remain covered by CI.