fix(opencode): preserve Astra priority service tier

[GuestAUser]

Issue for this PR

Closes #47506

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

Updates the bundled @ai-sdk/openai dependency from 3.0.84 to 3.0.88 in opencode and core. The older SDK excludes GPT-6 from its Priority capability check and removes service_tier: "priority" from otherwise valid Astra requests. The newer SDK recognizes it.

The regression goes through OpenCode's provider resolution and LLM.stream to a local HTTP endpoint. It checks Priority and Default with the canonical Astra model ID, max effort, an explicitly selected detailed summary, stateless encrypted reasoning, and tool replay/schema handling. The SDK package identity and authentication/transport code stay unchanged.

How did you verify your code works?

• Before: the new two-case regression had one pass and one failure on 3.0.84: Priority was undefined; Default and the preceding preservation assertions passed.
• After: 732 tests passed in the selected OpenCode suites below, including both new cases; another 7 passed in the core OpenAI provider suite. Both packages passed typechecking.
• Frozen-lockfile installation and formatting checks passed. The lockfile diff contains only the affected SDK pins/resolutions and their provider-utils dependency.

Commands ran with configuration/native-runtime environment overrides unset, using Bun 1.4.0:

# packages/opencode
bun test --timeout 30000 test/session/llm.test.ts test/provider/transform.test.ts test/provider/provider.test.ts test/plugin/openai-ws.test.ts test/plugin/auth-override.test.ts test/auth/auth.test.ts
bun typecheck

# packages/core
bun test --timeout 30000 test/plugin/provider-openai.test.ts
bun typecheck

# repository root
bun install --frozen-lockfile --ignore-scripts

The new Astra assertions use the API-key request path; existing auth, WebSocket, and cancellation checks passed unchanged. This verifies the requested tier, not live account entitlement or the tier ultimately granted by OpenAI. No production binary was built.

Screenshots / recordings

Not applicable; no UI changes.

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[opencode-agent]

Thanks for identifying this and verifying the SDK update. We are taking the dependency-only change forward in a separate PR, and have included you as a commit co-author. Closing this version to keep the implementation focused on the package bump.