[Feat] Add verified GPT-6 Astra support across providers

[zoomote]

​Opened on behalf of @navedmerchant. View the task or mention @roomote for follow-up asks.

What changed

• Adds GPT-6 Astra to native OpenAI and ChatGPT/Codex OAuth, including the Codex Responses Lite request contract and subscription eligibility metadata.
• Supports verified dynamic routes from LiteLLM, OpenRouter, NanoGPT, and Vercel AI Gateway while applying Astra's required reasoning, temperature, tool, cache, and token constraints.
• Preserves GPT-5.6 Sol as the default and leaves OpenCode Go and Zoo Code's current Amazon Bedrock transport unchanged because their available transport/catalog state does not safely support Astra.
• Expands focused coverage for request shaping, reasoning normalization, cache accounting, pricing, model discovery, and unsupported-route isolation.

Why this change was made

OpenAI released GPT-6 Astra in the API and for eligible ChatGPT Pro, Enterprise, and Business Premium users in Codex. Each provider exposes a different wire contract, so support is limited to routes verified through OpenAI's model documentation, the official Codex catalog, and live gateway catalogs.

Impact

Eligible users can select Astra through native OpenAI, ChatGPT/Codex OAuth, exact-route LiteLLM, OpenRouter, NanoGPT, or Vercel AI Gateway without changing the default model. Existing providers and model profiles keep their current behavior.

Screenshots

Related PRs

• Documentation: [Docs] Document GPT-6 Astra provider support Zoo-Code-Docs#59

[github-actions]

Review status

This PR was opened by an automated account. A human maintainer must verify the change intent, provenance, and validation before merging.

Current step: The required review sequence passed. Remaining merge requirements apply.

Review-state labels are managed by this workflow; do not edit them manually.

[codecov]

Codecov Report

❌ Patch coverage is 85.00000% with 15 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/api/providers/nanogpt.ts	77.77%	1 Missing and 3 partials ⚠️
src/api/providers/openai-native.ts	73.33%	0 Missing and 4 partials ⚠️
src/api/providers/openai-codex.ts	84.21%	1 Missing and 2 partials ⚠️
src/api/providers/vercel-ai-gateway.ts	76.92%	1 Missing and 2 partials ⚠️
src/api/providers/lite-llm.ts	95.00%	0 Missing and 1 partial ⚠️

📢 Thoughts on this report? Let us know!

[zoomote]

Completed the Astra provider follow-up for Naved Merchant. PR #1506 merged with native OpenAI, Codex OAuth/Responses Lite, exact-route LiteLLM, OpenRouter, NanoGPT, and Vercel support; paired docs remain in Zoo-Code-Docs #59.

The mutation gate failed during final validation because its direct-test selector omitted hyphen-suffixed suites. Since #1506 merged before that remediation finished, the validated CI/test fixes are isolated in draft follow-up #1530.

Validation: full tests passed (8,108 passed, 39 skipped), type checks and lint passed, mutation workflow tests passed, and the exact changed-code mutation gate passed locally with zero blockers. Follow-up CI is currently queued/in progress with no new failure reported.

Follow-up commits: 7773d4554, c673afbc5, and c59924987. View the task.