revert: Make Friendli the preferred provider for Z.ai models (#1178)

[kilo-code-bot]

Summary

Reverts #1178 which made Friendli the preferred provider for Z.ai models.

The revert restores:

• getPreferredProviderOrder to return only z-ai for Z.ai models (removing Friendli as the preferred provider)
• Removal of friendli from OpenRouterInferenceProviderIdSchema
• isZaiModel check back into shouldRouteToVercel to exclude Z.ai models from randomized Vercel routing

A conflict was resolved with a subsequent PR: !isOpenAiOssModel (added after #1178) is preserved alongside the restored !isZaiModel condition in shouldRouteToVercel.

Verification

• Branch compiles; typecheck pending CI run.

Visual Changes

N/A

Reviewer Notes

The revert was clean except for a minor conflict in src/lib/providers/vercel/index.ts where a later PR had added !isOpenAiOssModel(requestedModel). Both conditions are preserved in the resolved file.

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (3 files)

• src/lib/providers/index.ts
• src/lib/providers/openrouter/inference-provider-id.ts
• src/lib/providers/vercel/index.ts

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_{Reviewed by gpt-5.4-20260305 · 269,228 tokens}