feat(codex): gpt-5.5 support

[boggedbrush]

Summary

Adds GPT-5.5 support for Codex users and updates Codex model defaults/presets around the new model.

Changes

• Adds GPT-5.5 to Codex built-in models and aliases, with low reasoning effort as the default for GPT-5.5.
• Updates Codex default model handling across contracts, server account defaults, and app-server fallback paths.
• Refreshes Codex workflow starter presets for Free, Go, Plus, and Pro tiers.
• Keeps lower-tier utility/default generation paths on token-efficient GPT-5.4 Mini where appropriate.
• Removes Auto from Settings model pickers while preserving it for current thread/composer model selection.
• Fixes macOS desktop dev app identity/icon handling so the generated bundle uses the .icns asset and app.kodocode identifiers.

Testing

• bun fmt
• bun lint
• bun typecheck
• bun run test src/serverSettings.test.ts
• bun run test src/components/settings/SettingsModelsSection.test.tsx
• bun run test src/modelSelection.test.ts
• Additional focused server/shared/desktop tests were run while developing.

Notes

• Browser picker coverage for hiding Auto in persisted Settings pickers was added, but local browser-test execution was blocked because Playwright Chromium is not installed in this environment.