refactor(serve): split chat_completions endpoint into a package

[lvhan028]

Aligns with the responses/ package layout. Splits the 633-line chat_completions.py into protocol/validation/logprobs/logits_processors/ serving modules. Chat-specific models move to
endpoints/chat_completions/protocol.py; shared models stay in the top-level protocol.py with backward-compat re-exports. No behavior change.

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Motivation

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Modification

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BC-breaking (Optional)

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[Copilot]

Pull request overview

Refactors the OpenAI /v1/chat/completions endpoint implementation from a single large module into a dedicated chat_completions package, aligning its layout with the existing responses/ package and adding migration tests to enforce backward-compatible import paths.

Changes:

• Introduces lmdeploy.serve.openai.endpoints.chat_completions as a package with split-out protocol, validation, logprobs, logits_processors, and serving modules.
• Moves chat-specific Pydantic models into endpoints/chat_completions/protocol.py while keeping shared models in lmdeploy.serve.openai.protocol.
• Adds migration equivalence tests to assert package structure and re-export/class-identity invariants.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tests/test_chat_completions_package_migration.py	Adds structural migration tests for package layout + model re-export identity.
lmdeploy/serve/openai/protocol.py	Removes chat-specific models and re-exports them for backward compatibility.
lmdeploy/serve/openai/endpoints/chat_completions/validation.py	Extracts request validation logic for chat completions.
lmdeploy/serve/openai/endpoints/chat_completions/serving.py	Updates chat completions serving module to use the new split modules.
lmdeploy/serve/openai/endpoints/chat_completions/protocol.py	New canonical home for chat-specific Pydantic models.
lmdeploy/serve/openai/endpoints/chat_completions/logprobs.py	Extracts logprobs construction helpers.
lmdeploy/serve/openai/endpoints/chat_completions/logits_processors.py	Extracts logit-bias logits processor.
lmdeploy/serve/openai/endpoints/chat_completions/init.py	Adds lazy register export to avoid circular imports.
lmdeploy/serve/openai/endpoints/init.py	Adds lazy create_openai_router export to avoid circular imports.

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