refactor(sagemaker): move SageMaker transport to separate package

[lukeocodes]

Summary

• Move the SageMaker transport out of the SDK into a standalone deepgram-sagemaker package, since its AWS dependencies require Python >=3.12 but the SDK supports >=3.8
• Consolidate the README's "Custom WebSocket Transport" and "SageMaker Transport" sections into a single "Custom Transports" section that explains the concept, shows how to build one (sync + async), and uses deepgram-sagemaker as the real-world example
• Remove unused imports (JSONDecodeError, websockets) from socket client files flagged by ruff F401

Changes

File	Change
src/deepgram/transports/sagemaker.py	Deleted — moved to deepgram-sagemaker package
src/deepgram/transports/__init__.py	Cleared SageMaker exports
pyproject.toml	Removed mypy overrides for AWS SDK modules
README.md	Consolidated custom transports section with deepgram-sagemaker example
examples/27-transcription-live-sagemaker.py	Updated imports and install instructions
src/deepgram/*/socket_client.py (×4)	Removed unused imports
.fernignore	Updated comments

Test plan

• ruff check src/ passes
• mypy src/deepgram/transports/ passes
• No remaining sagemaker/SageMaker references in src/deepgram/
• New deepgram-sagemaker package structure verified in ../deepgram-python-sdk-transport-sagemaker/

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR decouples the SageMaker transport from the core SDK by removing the built-in implementation (and its AWS dependency surface) and pointing users to a standalone deepgram-sagemaker transport package, while also cleaning up a few unused imports and related config/docs.

Changes:

• Remove the built-in SageMaker transport module and its exports from deepgram.transports.
• Update README + SageMaker example to use deepgram-sagemaker as the supported transport approach.
• Remove unused imports in several WebSocket socket clients and drop now-unneeded mypy AWS overrides.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/deepgram/transports/sagemaker.py	Deleted built-in SageMaker transport implementation (moved to external package).
src/deepgram/transports/__init__.py	Removes SageMaker exports and reframes package docs.
pyproject.toml	Removes mypy ignore overrides for AWS-related modules.
README.md	Consolidates custom transport docs and updates SageMaker guidance to deepgram-sagemaker.
examples/27-transcription-live-sagemaker.py	Updates example install/imports to the external deepgram-sagemaker package.
src/deepgram/speak/v1/socket_client.py	Removes unused imports flagged by ruff.
src/deepgram/listen/v2/socket_client.py	Removes unused imports flagged by ruff.
src/deepgram/listen/v1/socket_client.py	Removes unused imports flagged by ruff.
src/deepgram/agent/v1/socket_client.py	Removes unused imports flagged by ruff.
.fernignore	Updates comments to reflect refactor and import cleanup.

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