fix(graphql): Add changeCode field to ComponentComparison and FlagComparison

[sentry]

This PR addresses issue API-ESK, a GraphQLError: Cannot query field 'changeCode' on type 'ComponentComparison'.

The root cause was that the changeCode field was being queried by a client but was not defined in the GraphQL schema for either ComponentComparison or FlagComparison types, nor was it implemented in their respective resolvers.

To fix this, the changeCode: Float field has been added to:

• apps/codecov-api/graphql_api/types/component_comparison/component_comparison.graphql
• apps/codecov-api/graphql_api/types/flag_comparison/flag_comparison.graphql

Corresponding resolvers have been implemented in:

• apps/codecov-api/graphql_api/types/component_comparison/component_comparison.py
• apps/codecov-api/graphql_api/types/flag_comparison/flag_comparison.py

These resolvers calculate changeCode as the difference between head_totals.coverage and base_totals.coverage, returning None if either total or their coverage values are unavailable. While a similar concept exists as changeCoverage on the Comparison type, changeCode was used here to directly match the field name requested by the client query.

Legal Boilerplate

Look, I get it. The entity doing business as "Codecov" is owned by Harness, Inc. In 2026 Harness acquired Codecov and as a result Harness is going to need some rights from me in order to utilize my contributions in this PR. So here's the deal: I retain all rights, title and interest in and to my contributions, and by keeping this boilerplate intact I confirm that Harness can use, modify, copy, and redistribute my contributions, under Harness's choice of terms.

Fixes API-ESK

[codecov-notifications]

Codecov Report

❌ Patch coverage is 18.18182% with 18 lines in your changes missing coverage. Please review.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...types/component_comparison/component_comparison.py	18.18%	9 Missing ⚠️
...aphql_api/types/flag_comparison/flag_comparison.py	18.18%	9 Missing ⚠️

📢 Thoughts on this report? Let us know!

🚀 New features to boost your workflow:

• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[codecov]

Codecov Report

❌ Patch coverage is 18.18182% with 18 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.80%. Comparing base (d8942db) to head (63df12f).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...types/component_comparison/component_comparison.py	18.18%	9 Missing ⚠️
...aphql_api/types/flag_comparison/flag_comparison.py	18.18%	9 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1874      +/-   ##
==========================================
- Coverage   91.83%   91.80%   -0.04%     
==========================================
  Files        1332     1332              
  Lines       51830    51852      +22     
  Branches     1647     1647              
==========================================
+ Hits        47598    47602       +4     
- Misses       3911     3929      +18     
  Partials      321      321              

Flag	Coverage Δ
apiunit	94.67% <18.18%> (-0.09%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

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