refactor(react): audit remaining compiler-era memoization and add guardrails

[BleedingDev]

Context

PR #482 removed redundant manual memoization made unnecessary by React Compiler, while preserving memoization that protects semantic identity for effects, state sync, external editors, and integration boundaries. Follow up with a smaller audit so future PRs do not reintroduce performance-only useMemo / useCallback / memo patterns in compiled apps.

Depends On

• PR Enable React Compiler across apps #482 merged

Scope

• Audit remaining useMemo, useCallback, and memo usage in compiled React app surfaces.
• Keep memoization where it is required for semantics, for example:
  • dependency identity used by effects that update state
  • editor/plugin instances
  • external library contracts
  • intentionally stable callback identity passed outside React
• Remove only clearly redundant performance-only memoization.
• Add a short convention note or local guideline if the repo has an appropriate place for it.
• Do not mix this with Next version upgrades or Rust compiler migration.

Validation

• Run focused lint/tests for touched apps.
• Run Nx affected lint/test locally under repo Node 24 before pushing.
• Confirm review bots have 0 unresolved comments.

Acceptance Criteria

• Remaining manual memoization is either removed or intentionally justified by surrounding code.
• New guideline/notes make the distinction clear for future compiler-era changes.
• CI is green.