Move change calculation into separate reducer

[langdal]

No description provided.

[Copilot]

Pull request overview

This PR refactors the change detection logic by moving it from the experimentReducer into a separate calculateChangeReducer, addressing a race condition where changes were not detected when a datapoint transitioned from invalid to valid state.

Changes:

• Extracted change calculation logic into a dedicated reducer
• Applied the new reducer after validation to ensure changes are detected post-validation
• Added comprehensive test coverage for the new reducer

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
packages/core/src/context/experiment/reducers.ts	Imports and applies the new calculateChangeReducer after validation
packages/core/src/context/experiment/reducers.test.ts	Adds test assertion to verify hash calculation consistency
packages/core/src/context/experiment/experiment-reducers.ts	Removes the change calculation logic from the main experiment reducer
packages/core/src/context/experiment/calculate-change-reducer.ts	New file containing the extracted change calculation logic
packages/core/src/context/experiment/calculate-change-reducer.test.ts	Comprehensive test suite for the new reducer
.changeset/silent-feet-breathe.md	Documents the fix for the race condition

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