[v2] Perf: Use one atom subscription per Field

[scttcper]

Each React Field subscribed to the same atom twice, once for value and once for meta. The field atom already preserves state identity when neither changes, so use one whole-state subscription instead.

This cuts active subscriptions from two to one per field with the same render behavior.

Summary by CodeRabbit

• Bug Fixes

  • Improved form field subscription handling to ensure updates are tracked consistently.
  • Preserved existing field API behavior while reducing redundant subscriptions.

• Tests

  • Updated subscription coverage to verify that each field uses a single active subscription.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: 0a39663b-a480-4f99-8fc7-ee3214ee7cf4

📥 Commits

Reviewing files that changed from the base of the PR and between 4ad5a7b and 45ed204.

📒 Files selected for processing (2)

• packages/react-form/src/ReactForm/fieldSubscriptions.lib.ts
• packages/react-form/tests/FormGroup.spec.tsx

Included review availability: Your plan provides up to 8 included reviews per hour; 7 remain after this review.

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📝 Walkthrough

Walkthrough

The field subscription now observes the complete field state through one subscription. The field-context test description and expected active subscription count reflect this change.

Changes

Field subscription update

Layer / File(s)	Summary
Unify field state subscription packages/react-form/src/ReactForm/fieldSubscriptions.lib.ts, packages/react-form/tests/FormGroup.spec.tsx	useValueFieldSubscription subscribes to full field state and tracks that state for memoization. The test expects one active AppForm field-provider subscription.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to 45ed2

This localized performance change reduces each field's atom subscriptions from two to one while preserving the stated render behavior; no actionable merge-blocking risk remains after normal checks and review.

Suggested reviewers: lecarbonator

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The description explains the change and motivation but omits the required Changes, Checklist, and Release Impact sections.	Add the required template sections, complete the checklist, and indicate whether a changeset is required.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly describes the main performance change: reducing Field atom subscriptions from two to one.
Docstring Coverage	✅ Passed	Docstring check was indeterminate for this PR — some files could not be analyzed in time. Not blocking.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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