task(sdk): Fix React hooks lint violations before upgrading eslint-plugin-react-hooks to v7

Description

eslint-plugin-react-hooks v7 introduces stricter lint rules (react-hooks/set-state-in-effect, react-hooks/immutability, react-hooks/refs) that cause 11 lint errors across sdk-react and sdk-experiments.

The upgrade from 5.0.0 → ^7.0.1 was attempted in the remove-unnused-libs-exports-imports-enum branch and had to be reverted to unblock CI. These violations need to be resolved before re-attempting the upgrade.

Approach: All violations must be resolved by refactoring to follow React best practices — no eslint-disable suppression. Tests must be added or updated for every refactored hook/component.

sdk-react (7 errors)

sdk-experiments (4 errors)

Acceptance Criteria

Refactoring (one per violation)

• DotCMSBlockEditorRenderer.tsx — Replace useState + useEffect with useMemo for block validation state
• Texts.tsx — Clone mark.attrs before mutating (rename class → className); no direct object mutation
• DotCMSEditableText.tsx:50 — Derive content state without synchronous setState inside useEffect
• DotCMSEditableText.tsx:56 — Derive initEditor state without synchronous setState inside useEffect
• useCheckVisibleContent.ts — Remove synchronous setState from useLayoutEffect
• useDotCMSShowWhen.ts — Replace useState + useEffect with useMemo
• useExperimentVariant.ts — Remove synchronous setShouldWaitForVariant() calls from useEffect
• memoize.ts — Refactor useMemoizedObject to avoid reading/writing ref.current during render

Quality gates

• All fixes use proper React patterns — no eslint-disable comments for these rules
• Tests added or updated for each refactored hook: useCheckVisibleContent, useDotCMSShowWhen, useMemoizedObject, useExperimentVariant
• Tests added or updated for refactored components: DotCMSBlockEditorRenderer, Texts.TextBlock, DotCMSEditableText
• eslint-plugin-react-hooks upgraded from 5.0.0 to ^7.0.1 in core-web/package.json
• yarn nx run sdk-react:lint passes with zero errors
• yarn nx run sdk-experiments:lint passes with zero errors
• yarn nx run sdk-react:test passes with zero failures
• yarn nx run sdk-experiments:test passes with zero failures

Priority

Medium

Additional Context

Reproduction:

# In core-web/package.json, change eslint-plugin-react-hooks to "^7.0.1"
yarn install
yarn nx affected -t lint --base=origin/main --exclude='tag:skip:lint'

Key references:

• eslint-plugin-react-hooks v7 changelog
• These new rules align with React Compiler expectations and encourage patterns that avoid cascading renders