[AadarshM07]

Summary

Closes #111

Implements the dependency-free CI file-length policy check and ratchet mechanism recommended in docs/investigations/file-length-limit.md:

• Enforces a 500 physical-line limit on tracked Python files in nitrostack/, tests/, examples/, and scripts/.
• Establishes a checked-in baseline (.file_length_baseline.json) for the 14 pre-existing legacy files that exceed 500 lines.
• Implements a one-way ratchet: existing files cannot grow past their baseline, and --update-baseline lowers the baseline as files shrink or graduates them when they reach ≤ 500 lines.
• Adds the check to .github/workflows/test.yml across the Python 3.10, 3.11, and 3.12 matrix.
• Documents the policy, definition, scope, exemptions, and ratchet workflow in CONTRIBUTING.md.

Changes

• scripts/check_file_lengths.py: Standard-library checker script with ratchet and baseline update logic.
• .file_length_baseline.json: Baseline manifest containing recorded line counts for the 14 legacy over-limit files.
• tests/test_file_length_check.py: Focused test suite covering 500-line boundary, new files > 500, baseline growth, ratchet lowering, and baseline graduation.
• .github/workflows/test.yml: Added step to execute python scripts/check_file_lengths.py before pytest.
• CONTRIBUTING.md: Developer guide explaining the policy, counting rules, and baseline update commands.