Add NanoGPT transcription provider

[BinkyTwin]

Summary

• add --api nanogpt backed by NanoGPT's OpenAI-compatible audio transcription endpoint
• document NANOGPT_API_KEY, NANOGPT_MODEL, NANOGPT_API_ENDPOINT, and NanoGPT chat correction configuration
• implement --correct for NanoGPT through NanoGPT's OpenAI-compatible chat endpoint
• add mocked unittest coverage for request wiring, missing configuration, correction, and CLI routing

Verification

• UV_PROJECT_ENVIRONMENT=/tmp/sapat-nanogpt-venv uv run python -m unittest tests.test_nanogpt
• python -m compileall src tests
• git diff --check

Companion Daytona content PR: daytonaio/content#242

[Copilot]

Pull request overview

This PR adds a new NanoGPT-backed transcription provider to the sapat CLI, using NanoGPT’s OpenAI-compatible audio transcription endpoint, and documents the required configuration.

Changes:

• Added NanoGPTTranscription provider wired into the CLI via --api nanogpt.
• Documented NanoGPT environment variables (NANOGPT_API_KEY, NANOGPT_MODEL, NANOGPT_API_ENDPOINT) and bumped minimum Python version to 3.8.
• Added unit tests covering NanoGPT request wiring, missing configuration, and CLI routing.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tests/test_nanogpt.py	Adds mocked unit tests for NanoGPT provider request wiring and CLI routing.
src/sapat/transcription/nanogpt.py	Implements NanoGPT OpenAI-compatible transcription provider.
src/sapat/script.py	Adds NanoGPT option to CLI provider selection.
README.md	Documents NanoGPT usage and environment variables; updates supported providers and Python version.
pyproject.toml	Raises requires-python to >=3.8 and retains needed dependencies (incl. python-dotenv).

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[BinkyTwin]

Follow-up after automated review:

• Implemented NanoGPT --correct support via NanoGPT's OpenAI-compatible chat completion endpoint (NANOGPT_CHAT_MODEL / NANOGPT_CHAT_ENDPOINT).
• Added mocked coverage for correction request wiring and missing chat model config; NanoGPT tests now cover request wiring, missing config, correction, and CLI routing.
• Re-ran local verification:
  • UV_PROJECT_ENVIRONMENT=/tmp/sapat-nanogpt-venv uv run python -m unittest tests.test_nanogpt
  • python -m compileall src tests
  • git diff --check

The three Continue status checks currently show Agent encountered an error; their target page returns Cannot GET /api/agent-check-summary/..., so I do not have actionable logs from those checks.