loro-extended-meta-container.md

@loro-extended/change	minor
@loro-extended/repo	minor

Add schema-level mergeable configuration and document metadata

• Shape.doc() now accepts an options parameter with mergeable?: boolean
• Document metadata is stored in _loro_extended_meta_ root container
• Metadata includes mergeable flag for peer agreement
• toJSON() excludes all _loro_extended* prefixed keys from output
• Reserved prefix _loro_extended for future internal use
• loro(doc).mergeable exposes the effective mergeable value
• Handle now exposes isMergeable getter (delegates to TypedDoc)
• New skipInitialize option to defer metadata writing
• New doc.initialize() method for manual metadata initialization

Usage:

const schema = Shape.doc({
  players: Shape.record(Shape.struct({ score: Shape.plain.number() })),
}, { mergeable: true })

// Auto-initialize (default) - writes metadata immediately
const doc = createTypedDoc(schema)

// Skip initialization for advanced use cases
const doc2 = createTypedDoc(schema, { skipInitialize: true })
// Later, when ready:
doc2.initialize()

// Access effective mergeable value
loro(doc).mergeable // true