docs: add VSCode+uv A-to-Z beginner guide; CLI/UI and analysis improvements

[rad1092]

Motivation

• Provide a complete A-to-Z beginner guide that starts from creating a folder in VSCode and covers uv venv creation, activation, install, Ollama setup, CLI and UI usage, and troubleshooting.
• Improve developer ergonomics for local testing by making pytest runnable without manually setting PYTHONPATH.
• Add first-class support for building analysis payloads from inline CSV text and make the CLI more flexible to run the UI or legacy analyze mode.

Description

• Rewrite BEGINNER_README.md into a step-by-step VSCode + uv A-to-Z guide including exact shell commands, activation steps, Ollama setup, CLI/UI flows, troubleshooting, and a completion checklist.
• Add build_prompt and build_analysis_payload_from_csv_text to bitnet_tools/analysis.py (and import io) and refactor build_analysis_payload to use the new prompt builder.
• Refactor CLI in bitnet_tools/cli.py to _build_parser/main, add a ui subcommand that delegates to serve, support legacy positional analyze invocation, and keep optional immediate ollama run execution via --model.
• Export the updated analysis API from bitnet_tools/__init__.py, add pythonpath = ["."] to [tool.pytest.ini_options] in pyproject.toml, and add/update tests in tests/test_analysis.py and new tests/test_cli.py.

Testing

• Ran pytest -q and the suite completed successfully with 5 passed.
• Ran python -m bitnet_tools.cli --help which printed CLI usage and exited successfully.
• The added CLI and analysis tests (tests/test_cli.py, expanded tests/test_analysis.py) were included in the test run and passed.

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Codex Task