Temporarily downgrade Claude to 3.5 Sonnet

[anth-volk]

Fixes #2519.

What Changed

• Temporarily downgraded Claude to 3.5 Sonnet

Why This Change

• Claude 4.0 sometimes inserts unwanted quotes into Explain with AI outputs (see Post-upgrade to Claude Sonnet 4.0, Claude sometimes inserts unwanted quotes into the Explain with AI feature policyengine-app#2584); we don't want to fully downgrade from Claude 4.0, but we want to temporarily prevent the quotes issue, then re-upgrade and add a more durable fix.

Technical Details

N/A

[anth-volk]

Will merge upon test passage

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 63.62%. Comparing base (2abc9bb) to head (8b08421).
Report is 67 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2520   +/-   ##
=======================================
  Coverage   63.62%   63.62%           
=======================================
  Files          56       56           
  Lines        2161     2161           
  Branches      287      287           
=======================================
  Hits         1375     1375           
  Misses        729      729           
  Partials       57       57           

☔ View full report in Codecov by Sentry.
📢 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.