docs: document --format report types and CSV header-only behavior (#132)

[gitcommit90]

Summary

• Add a Report formats subsection with a table describing the four --format types.
• Explicit note on zero-finding CSV headers.
• Cross-links to Machine-readable output and JSON Schema sections.

Closes #132

[github-actions]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.51%. Comparing base (a2fe184) to head (cbe5cc3).
⚠️ Report is 30 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #141      +/-   ##
==========================================
+ Coverage   78.95%   80.51%   +1.56%     
==========================================
  Files          26       32       +6     
  Lines        4158     5169    +1011     
==========================================
+ Hits         3283     4162     +879     
- Misses        875     1007     +132     

Flag	Coverage Δ
unittests	80.51% <ø> (+1.56%)	⬆️

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[advaitpatel]

lgtm