Enable docstring linting and add missing docstrings to public API

[jtdub]

Description

The project's pyproject.toml currently suppresses docstring requirements:

• ruff: D100-D107 (missing docstrings) are in the ignore list, tagged "should eventually be enabled"
• pylint: missing-class-docstring, missing-function-docstring, missing-module-docstring are disabled

As a result, many key public methods lack docstrings:

• HConfigBase.config_to_get_to()
• HConfigBase._future() (only has a note about known gaps, no usage docs)
• HConfigBase.unified_diff()
• HConfigChild.negate()
• HConfigChild.is_match() (has a docstring but no Args/Returns)
• HConfigChild.overwrite_with()
• HConfigChild class itself
• HConfigChildren class
• Most platform driver classes

Proposed Improvement

1. Incrementally enable D101 (public class), D102 (public method), D103 (public function) in ruff
2. Add docstrings to the highest-impact public methods first (the ones listed above)
3. Use a consistent format (Google style or NumPy style) with Args/Returns sections for complex signatures
4. Re-enable the corresponding pylint checks

The project already has excellent docstrings on WorkflowRemediation, RemediationReporter, and utility functions — extending that standard to the rest of the public API would significantly improve developer experience.