@fourjs/serialization

Scene serialization and migrations. Part of fourJS.

Implements §79–80 of docs/SPECIFICATION.md; shipped in Phase 11 (§113a). Documents are versioned (SCENE_FORMAT_VERSION = 1), canonical, and diff-friendly; round trips are byte-identical.

What's here

• Format — SceneDocument / SceneNodeDocument / ComponentDocument types, encodeSceneDocument / decodeSceneDocument (canonical JSON text), and validators (validateSceneDocument, transform/vector/quaternion document validation).
• §96 untrusted text — decodeSceneDocument(text, limits?) takes UntrustedJsonLimits (maximumTextLength, maximumDepth; finite defaults) and refuses an over-budget or over-deep document with UNTRUSTED_INPUT_REJECTED before validateNode recurses. validateSceneDocument is deliberately unguarded — it takes values, not text.
• Serializer — serializeScene / instantiateScene over a ComponentSerializerRegistry keyed by component class; createDefaultComponentSerializers covers the built-in components (including PoseTarget).
• Migrations (§80) — SceneMigration / SceneMigrationRegistry, migrateSceneDocument / runSceneMigrations, with structured warnings.
• JSON utilities — JsonValue guards (isJsonObject, isJsonArray, asJsonObject) and cloneJsonValue (re-exported from @fourjs/core, __proto__-refusing).

Known boundaries / staged

• Components without a registered serializer are silently unsaved (documented boundary); restored node ids can collide with the live counter.
• §79 documents deliberately do not carry solver warm-start state — a contact-free save replays bit-identically, an in-contact save diverges only through warm-start; §34 snapshots (@fourjs/diagnostics) carry that state.
• The binary .four format is not implemented; the JSON document is the shipped format.

Unit tests are colocated in tests/ per §92.

Workspace name @fourjs/serialization; publishes as @danielsimonjr/fourjs-serialization.