Fix #129: Auto-generate config dumps from Pydantic models

[Devguru-codes]

Hello @ltorres6 sir, I saw the issue and I have worked on it. This PR refactors the CLI configuration dumping mechanism to automatically generate YAML templates directly from the Pydantic model schemas, permanently eliminating drift between hard-coded strings and the actual schemas.
The changes that i have made are -

1. Automated Generator:- Replaced the hard-coded _DEFAULT_TEMPLATES dictionary in config.py with an introspection function (_generate_section_yaml) that dynamically builds the YAML hierarchy based on model_fields.

2. Documentation Injection:- Added Field(default=..., description=...) parameters to over 50 model attributes. These descriptions are automatically parsed and appended as inline comments to guide the user (e.g., te: 30.0 # echo time (ms)).

3. Structure Maintained:- The outputs remain grouped logically. Active fields map to their defaults, while Optional settings defaulting to None are neatly emitted as commented-out lines (e.g., # flip_angles: null).

4. Anti-Drift Guardrails:- Added a new parameterised test (test_dump_defaults_covers_all_model_fields) to guarantee that any field added to a Pydantic model in the future mechanically shows up in the auto-generated templates.
   The new tests will help catch configuration mismatches and prevent any similar issues going forward.

I will wait for your response. If you think this pr needs any updates, please tell me and I will implement it. Thank you.
Fixes #129