chore(models): use GPT-6 Luna for text generation

[extoci]

What Changed

• Use gpt-6-luna as the default Codex text generation model, retaining low reasoning effort.
• Remove the settings test that repeated the hardcoded default.

Why

The model manifest already lists GPT-6 Luna as a current Codex model. New settings should select it automatically, while saved model choices remain intact. The removed test asserted the configuration literal rather than observable behavior.

Verification

• vp test run packages/contracts/src/settings.test.ts apps/server/src/serverSettings.test.ts (188 tests passed)
• pnpm --filter @t3tools/contracts typecheck
• Targeted lint and formatting checks passed.

Checklist

• This PR is small and focused
• I explained what changed and why

Model: GPT-6 Astra; harness: Codex.

Summary by CodeRabbit

• Updates
  • The default text-generation model has been updated from GPT-5.6 Luna to GPT-6 Luna.
  • New text-generation configurations will use GPT-6 Luna by default unless a different model is selected.

[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — This PR changes the production default text-generation model used for new settings and fallback selection, while removing the direct test for the previous default. Although the code change is small and persisted choices are preserved, product-default changes require human review.

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ℹ️ Recent review info

⚙️ Run configuration

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📥 Commits

Reviewing files that changed from the base of the PR and between 83bbfa7 and cbcd677.

📒 Files selected for processing (2)

• packages/contracts/src/model.ts
• packages/contracts/src/settings.test.ts

💤 Files with no reviewable changes (1)

• packages/contracts/src/settings.test.ts

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📝 Walkthrough

Walkthrough

The Codex text generation default changes from gpt-5.6-luna to gpt-6-luna. The settings test that asserted the previous model value is removed.

Changes

Codex model default

Layer / File(s)	Summary
Model default and validation packages/contracts/src/model.ts, packages/contracts/src/settings.test.ts	The default text generation model changes to gpt-6-luna. The test asserting gpt-5.6-luna is removed.

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~3 minutes

Change: Bug fix

Suggested reviewers: juliusmarminge

Merge Risk: 🔵 Low · up to cbcd6

The change is mergeable, but a focused settings-default regression assertion would reduce the risk of silently selecting the wrong model later.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description check	✅ Passed	The description clearly explains the model change, the reason, and verification results. It covers the required What Changed and Why sections and confirms that the PR is small and focused. The UI Chan…
Title check	✅ Passed	The title clearly and concisely identifies the main change: using GPT-6 Luna for text generation.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 1…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create a new PR

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