feat: Update Agent helm chart for redhat openshift helm registry

[anandrkskd]

Assisted by: Cursor

What does this PR do / why we need it:

This PR updates the Argo CD agent helm chart to make it OpenShift helm chart registry ready for downstream release. It adds values.schema.json and adds README using helm-docs CLI.

Which issue(s) this PR fixes:

Fixes #

How to test changes / Special notes to the reviewer:

Checklist

• Documentation update is required by this PR (and has been updated) OR no documentation update is required.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 45.62%. Comparing base (94295a6) to head (0f13dc5).
⚠️ Report is 12 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #590      +/-   ##
==========================================
+ Coverage   44.52%   45.62%   +1.10%     
==========================================
  Files          90       90              
  Lines       11909    12021     +112     
==========================================
+ Hits         5302     5485     +183     
+ Misses       6174     6091      -83     
- Partials      433      445      +12     

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