Add GPT-5.6 Sol, Terra, and Luna to Codex models

[thstyl2000]

The manually maintained openai-codex model list currently stops at GPT-5.5.

OpenAI now exposes GPT-5.6 Sol, Terra, and Luna in Codex, however adding the three canonical model IDs to the existing Codex model list and regenerating models.generated.ts, does not work. Possibly due to newer metadata for these models.

[codehearted]

I'm hitting the same class of problem from the Anthropic side. Claude Opus 4.8, Sonnet 5, and Fable 5 are all missing from the registry, and I dug into why regeneration isn't picking new models up. Findings:

1. The auto-update-models workflow has failed every day since it was introduced (Jun 21). It's not the generator itself: the workflow regenerates fine, then dies at the "Build + test (gate release)" step because the TUI test suite is broken on main. E.g. packages/tui/test/scroll-buffer.test.ts imports vitest but the suite runs under node --test --import tsx, which crashes with "Vitest failed to access its internal state", plus ~8 other failing assertions (overlay-short-content, spinner/redraw tests). Since the gate blocks the commit, the catalog never refreshes, which would explain why manually adding IDs and regenerating locally is the only thing that works right now.

2. Separately, the PR Gate workflow crashes with an unhandled 404: it reads .github/APPROVED_CONTRIBUTORS, but that file is currently named APPROVED_CONTRIBUTORS.vacation on main. So new-contributor PRs (e.g. Add missing models for Claude Opus 4.8 and Sonnet 5 #49, which adds Opus 4.8 and Sonnet 5) neither pass the check nor get the auto-close message.

Fixing the TUI tests (or excluding them from the auto-update gate) would let the daily refresh pick all of this up automatically, likely including the GPT-5.6 models here.