Remove z.ai provider (extracted to req_llm_zai)

[Nickcom4]

Summary

• Extracts Z.AI provider into standalone package req_llm_zai
• Removes zai, zai_coder, and zai_coding_plan provider modules from core
• Removes associated tests, coverage tests, and guide docs
• Updates mix.exs docs config to remove z.ai guide references

Files Removed

• lib/req_llm/providers/zai.ex (531 lines)
• lib/req_llm/providers/zai_coder.ex (532 lines)
• lib/req_llm/providers/zai_coding_plan.ex (101 lines)
• test/providers/zai_test.exs (58 lines)
• test/coverage/zai/comprehensive_test.exs
• test/coverage/zai_coder/comprehensive_test.exs
• guides/zai.md (43 lines)
• guides/zai_coder.md (47 lines)

Remaining z.ai references (intentionally kept)

• lib/req_llm/provider/generated/valid_providers.ex - auto-generated from LLMDB model catalog, z.ai models still exist there
• google_vertex and venice providers/tests - these reference z.ai-org models hosted on those platforms, not the z.ai provider itself

Migration Path

Users add {:req_llm_zai, "~> 0.1.0"} to their deps. The new package auto-registers all three providers on application start via ReqLLM.Providers.register/1. No code changes needed beyond adding the dependency.

Test plan

• req_llm_zai compiles cleanly with req_llm ~> 1.6 as dependency
• All 12 tests pass in the new package (original 2 + 10 new)
• Core ReqLLM tests still pass after removal (2160 tests, 0 failures)
• Verified no remaining z.ai provider code references in core (only LLMDB model catalog and cross-platform model IDs)

[mikehostetler]

Blocking note for release: we can’t ship this with a Git dependency, since ReqLLM itself is published on Hex and downstream users should install via Hex only. We need req_llm_zai published to Hex before merging this extraction.

Once it’s published, I can add a ZAI key and run a quick live validation pass.

[Nickcom4]

Published to Hex: https://hex.pm/packages/req_llm_zai/0.1.0

Docs at: https://hexdocs.pm/req_llm_zai/0.1.0

Ready for your live validation pass whenever you get a chance.

[mikehostetler]

Cool - happy to accept the transfer to the org - let's
Sync in Discord so we have a clean handoff

[mikehostetler]

@Nickcom4 if you want to initiate the github transfer, should be ready for that - and then lets discuss how to transition hex keys so I can deploy - thx