fix(core): preserve movable root containers from initial state

[lodyai]

Summary

• Make initialState root container pre-creation use schema type when available, otherwise reuse the same inference choice as setState.
• Respect inferOptions.defaultMovableList for root arrays so Mirror does not create a root List before later writing to a same-name MovableList.
• Add a snapshot round-trip regression test for initialState + defaultMovableList.

Tests

• pnpm exec vitest run packages/core/tests/mirror-movable-list.test.ts
• pnpm --filter loro-mirror test
• pnpm --filter loro-mirror typecheck
• pnpm --filter loro-mirror build
• pnpm exec oxlint --type-aware packages/core/src/core/mirror.ts packages/core/tests/mirror-movable-list.test.ts

Notes

• Refs Exporting snapshot exports data incorrectly loro#972.
• Full pnpm lint still fails on existing unused-variable issues in packages/core/tests/transform-error-handling.test.ts, unrelated to this change.