feat: add init questionnaire command

[fmueller]

Motivation

• Provide a guided, consistent CLI flow to create a project scribae.yaml so users can set sensible defaults for Scribae commands.
• Support writing the config into a project folder or a custom filename and align UX with existing commands (prompts, colors, examples).

Description

• Add a new scribae init CLI command implemented in src/scribae/init_cli.py that runs a terminal questionnaire and renders a scribae.yaml file.
• Support --project <folder> (creates folder if needed) and --file <filename> output targets and validate the two options are mutually exclusive.
• Ask the user before overwriting existing files, with a --force option to skip confirmation, and produce friendly colored prompts and examples for each field.
• Normalize list inputs (comma-separated keywords / allowed tags) and render YAML using yaml.safe_dump while preserving order.
• Register the command in the CLI entrypoint by adding init to src/scribae/main.py and add unit tests in tests/unit/init_cli_test.py covering default file, project directory, custom file, overwrite prompt, --force, and option validation.

Testing

• Ran uv run ruff check and all checks passed.
• Ran uv run mypy which surfaced environment-related import issues for optional ML dependency (torch) unrelated to the new init command; these are external to the change.
• Ran uv run pytest and all unit tests passed (166 passed).

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Codex Task