Document hook stage file input

[j178]

Closes #2144

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.52%. Comparing base (0fa2929) to head (af1a523).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2147   +/-   ##
=======================================
  Coverage   92.51%   92.52%           
=======================================
  Files         122      122           
  Lines       26016    26016           
=======================================
+ Hits        24070    24071    +1     
+ Misses       1946     1945    -1     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[Copilot]

Pull request overview

This PR updates the documentation to clearly define what input (repository file paths vs. no files vs. message file) each supported Git hook stage receives, so users understand when file filters (files, types, etc.) apply and when always_run: true is required.

Changes:

• Adds a “Supported Git Hook Stages” reference section describing stage semantics and hook input.
• Cross-links the stages / default_stages configuration docs to that stage semantics section.
• Updates hook authoring docs to point hook authors to the stage semantics reference.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
docs/reference/configuration.md	Adds a stage semantics table and links from stages/default_stages to clarify hook input and filtering behavior.
docs/authoring-hooks.md	Links hook authors to the stage semantics reference for correct stage selection and expectations.