fix: batch parent saves during live array resets

[moimikey]

Overview

Item	Value
PR	#53
Goal	Persist a live-array parent once per refetch reset instead of once per child-reference mutation. FEPLAT-5145
Risk profile	Low; REMEDIATION. Internal persistence control only, with add-before-remove retention covered by regression tests.
Rollout order	Merge this upstream remediation first; downstream Fetchium release and wallet adoption are TBD.

What Changed

Area	Files	Change	Why
Entity references	packages/fetchium/src/EntityInstance.ts	Allow child-reference updates to skip immediate persistence.	Prevent each reset item from serializing and writing the full parent.
Live arrays	packages/fetchium/src/LiveCollection.ts	Suppress intermediate saves while preserving add-before-remove ordering.	The existing entity-apply boundary persists the completed parent once.
Regression coverage	packages/fetchium/src/__tests__/live-array.test.ts	Assert one parent save, stable shared-child identity, and retained reference count after refetch.	Prove batching does not weaken reference safety.

Findings Addressed

Finding	Status	Resolution
Parent serialized and persisted once per added or removed reset item.	Resolved	Reset reference mutations defer persistence to the final entity-apply save.
Batching could evict a child present in both old and new arrays.	Covered	Add-before-remove ordering remains unchanged and the regression test verifies identity and reference count.

Validation

Command	Result
npm run test:unit -w fetchium -- src/__tests__/live-array.test.ts	RED: observed 5 parent saves instead of 1; GREEN: 18/18 tests passed.
npm run test:unit -w fetchium	1,172 passed; 2 skipped.
npm run check-types -w fetchium	Passed.
npm run lint	ESLint and Prettier checks passed.
npm run build -w fetchium	Passed for types, development, and production builds.
npm test -w fetchium	Browser-inclusive run unavailable locally: Chromium headless shell was missing, and two installation attempts hung after reaching 100% download. Unit tests were run separately and passed.

Merge Sequencing

Step	PR
1	This upstream REMEDIATION PR; no upstream PR dependency.
2	Fetchium release and downstream wallet adoption: TBD.