fix(core): recompute field-array dirty state

[RtlZeroMemory]

Summary

• recompute field-array dirty state from the next array snapshot after append/remove/move
• preserve scalar array-level errors when structural edits happen with validateOnChange: false
• tighten field-array regressions around length-mismatch dirty semantics and scalar error preservation

Testing

• npm run build
• npm run lint
• npm run typecheck
• node scripts/run-tests.mjs --filter "form.fieldArray"
• node scripts/run-tests.mjs --filter "useForm"

Summary by CodeRabbit

Bug Fixes

• Fixed dirty state tracking for field arrays to accurately reflect changes after append, remove, or move operations.
• Fixed preservation of array-level errors when validation on change is disabled.

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[coderabbitai]

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 8276eb8c-b9bf-4930-a7f3-4f172212d9ee

📥 Commits

Reviewing files that changed from the base of the PR and between 2980659 and 15a0d1f.

📒 Files selected for processing (3)

• CHANGELOG.md
• packages/core/src/forms/__tests__/form.fieldArray.test.ts
• packages/core/src/forms/internal/arrayState.ts

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📝 Walkthrough

Walkthrough

This PR fixes the dirty state recomputation for field arrays after append, remove, and move operations, and ensures array-level scalar errors are preserved when validateOnChange is disabled. Changes include a new error remapping helper, refactored dirty-state logic using computeFieldDirty, and comprehensive regression tests.

Changes

Cohort / File(s)	Summary
Documentation CHANGELOG.md	Added entries documenting bug fixes for useFieldArray dirty state recomputation and error preservation, plus regression test additions.
Tests packages/core/src/forms/__tests__/form.fieldArray.test.ts	Updated test expectations from per-item dirty arrays to scalar boolean values; added regression tests for array-level error preservation across append/remove/move operations when validateOnChange is disabled.
Core Logic packages/core/src/forms/internal/arrayState.ts	Introduced remapFieldArrayErrors helper for consistent error array mapping; replaced manual dirty-tracking with computeFieldDirty-based updates; refactored error preservation logic in append, remove, and move operations.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Poem

🐰 Dirty states now recompute clean,
Arrays remember errors unseen,
Append and remove with grace,
Scalar errors find their place,
Field arrays hop along serene! ✨

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title directly and concisely describes the main change: recomputing field-array dirty state, which aligns with the PR's primary objective and the modifications across the codebase.

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✨ Finishing Touches

• 📝 Generate docstrings (stacked PR)
• 📝 Generate docstrings (commit on current branch)

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch codex/fix-form-array-dirty-errors

📝 Coding Plan

• Generate coding plan for human review comments

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